Always check weak global references before using them

We hold weak references to Java objects from native code in several
places to avoid circular reference problems. These objects may become
weakly reachable at any time, after which the GC could null our weak
reference, so we have to null-check at every use.

Note that weak references are nulled before the referent is finalized,
so we can't rely on doing work in the finalizer to wait for the
currently executing message to complete and to remove other messages
from the queue.

This effectively reverts
https://android-git.corp.google.com/g/#change,30955

Bug: 4336862
Change-Id: I431fcac11220cb406c26e31aacb9bda7ea22776e

1 files changed, 69 insertions, 32 deletions

diff --git a/Source/WebKit/android/nav/WebView.cpp b/Source/WebKit/android/nav/WebView.cpp
index f56cd69..2494399 100644
--- a/Source/WebKit/android/nav/WebView.cpp
+++ b/Source/WebKit/android/nav/WebView.cpp
@@ -359,11 +359,13 @@ void scrollRectOnScreen(const IntRect& rect)
 void calcOurContentVisibleRect(SkRect* r)
 {
     JNIEnv* env = JSC::Bindings::getJNIEnv();
+    AutoJObject javaObject = m_javaGlue.object(env);
+    if (!javaObject.get())
+        return;
     jclass rectClass = env->FindClass("android/graphics/RectF");
     jmethodID init = env->GetMethodID(rectClass, "<init>", "(FFFF)V");
     jobject jRect = env->NewObject(rectClass, init, 0, 0, 0, 0);
-    env->CallVoidMethod(m_javaGlue.object(env).get(),
-        m_javaGlue.m_calcOurContentVisibleRectF, jRect);
+    env->CallVoidMethod(javaObject.get(), m_javaGlue.m_calcOurContentVisibleRectF, jRect);
     r->fLeft = env->GetFloatField(jRect, m_javaGlue.m_rectFLeft);
     r->fTop = env->GetFloatField(jRect, m_javaGlue.m_rectFTop);
     r->fRight = r->fLeft + env->CallFloatMethod(jRect, m_javaGlue.m_rectFWidth);
@@ -726,9 +728,11 @@ CachedRoot* getFrameCache(FrameCachePermission allowNewer)
             // The focus has changed.  We may need to update things.
             LOG_ASSERT(m_javaGlue.m_obj, "A java object was not associated with this native WebView!");
             JNIEnv* env = JSC::Bindings::getJNIEnv();
-            env->CallVoidMethod(m_javaGlue.object(env).get(),
-                    m_javaGlue.m_domChangedFocus);
-            checkException(env);
+            AutoJObject javaObject = m_javaGlue.object(env);
+            if (javaObject.get()) {
+                env->CallVoidMethod(javaObject.get(), m_javaGlue.m_domChangedFocus);
+                checkException(env);
+            }
         }
     }
     if (oldCursorNode && (!m_frameCacheUI || !m_frameCacheUI->currentCursor()))
@@ -740,7 +744,10 @@ int getScaledMaxXScroll()
 {
     LOG_ASSERT(m_javaGlue.m_obj, "A java object was not associated with this native WebView!");
     JNIEnv* env = JSC::Bindings::getJNIEnv();
-    int result = env->CallIntMethod(m_javaGlue.object(env).get(), m_javaGlue.m_getScaledMaxXScroll);
+    AutoJObject javaObject = m_javaGlue.object(env);
+    if (!javaObject.get())
+        return 0;
+    int result = env->CallIntMethod(javaObject.get(), m_javaGlue.m_getScaledMaxXScroll);
     checkException(env);
     return result;
 }
@@ -749,7 +756,10 @@ int getScaledMaxYScroll()
 {
     LOG_ASSERT(m_javaGlue.m_obj, "A java object was not associated with this native WebView!");
     JNIEnv* env = JSC::Bindings::getJNIEnv();
-    int result = env->CallIntMethod(m_javaGlue.object(env).get(), m_javaGlue.m_getScaledMaxYScroll);
+    AutoJObject javaObject = m_javaGlue.object(env);
+    if (!javaObject.get())
+        return 0;
+    int result = env->CallIntMethod(javaObject.get(), m_javaGlue.m_getScaledMaxYScroll);
     checkException(env);
     return result;
 }
@@ -759,7 +769,10 @@ IntRect getVisibleRect()
     IntRect rect;
     LOG_ASSERT(m_javaGlue.m_obj, "A java object was not associated with this native WebView!");
     JNIEnv* env = JSC::Bindings::getJNIEnv();
-    jobject jRect = env->CallObjectMethod(m_javaGlue.object(env).get(), m_javaGlue.m_getVisibleRect);
+    AutoJObject javaObject = m_javaGlue.object(env);
+    if (!javaObject.get())
+        return rect;
+    jobject jRect = env->CallObjectMethod(javaObject.get(), m_javaGlue.m_getVisibleRect);
     checkException(env);
     rect.setX(env->GetIntField(jRect, m_javaGlue.m_rectLeft));
     checkException(env);
@@ -1083,9 +1096,11 @@ int getBlockLeftEdge(int x, int y, float scale)
 void overrideUrlLoading(const WTF::String& url)
 {
     JNIEnv* env = JSC::Bindings::getJNIEnv();
+    AutoJObject javaObject = m_javaGlue.object(env);
+    if (!javaObject.get())
+        return;
     jstring jName = wtfStringToJstring(env, url);
-    env->CallVoidMethod(m_javaGlue.object(env).get(),
-            m_javaGlue.m_overrideLoading, jName);
+    env->CallVoidMethod(javaObject.get(), m_javaGlue.m_overrideLoading, jName);
     env->DeleteLocalRef(jName);
 }
 
@@ -1205,8 +1220,10 @@ void sendMoveFocus(WebCore::Frame* framePtr, WebCore::Node* nodePtr)
 {
     DBG_NAV_LOGD("framePtr=%p nodePtr=%p", framePtr, nodePtr);
     JNIEnv* env = JSC::Bindings::getJNIEnv();
-    env->CallVoidMethod(m_javaGlue.object(env).get(),
-        m_javaGlue.m_sendMoveFocus, (jint) framePtr, (jint) nodePtr);
+    AutoJObject javaObject = m_javaGlue.object(env);
+    if (!javaObject.get())
+        return;
+    env->CallVoidMethod(javaObject.get(), m_javaGlue.m_sendMoveFocus, (jint) framePtr, (jint) nodePtr);
     checkException(env);
 }
 
@@ -1214,8 +1231,10 @@ void sendMoveMouse(WebCore::Frame* framePtr, WebCore::Node* nodePtr, int x, int
 {
     DBG_NAV_LOGD("framePtr=%p nodePtr=%p x=%d y=%d", framePtr, nodePtr, x, y);
     JNIEnv* env = JSC::Bindings::getJNIEnv();
-    env->CallVoidMethod(m_javaGlue.object(env).get(), m_javaGlue.m_sendMoveMouse,
-        (jint) framePtr, (jint) nodePtr, x, y);
+    AutoJObject javaObject = m_javaGlue.object(env);
+    if (!javaObject.get())
+        return;
+    env->CallVoidMethod(javaObject.get(), m_javaGlue.m_sendMoveMouse, reinterpret_cast<jint>(framePtr), reinterpret_cast<jint>(nodePtr), x, y);
     checkException(env);
 }
 
@@ -1223,21 +1242,24 @@ void sendMoveMouseIfLatest(bool clearTextEntry, bool stopPaintingCaret)
 {
     LOG_ASSERT(m_javaGlue.m_obj, "A java object was not associated with this native WebView!");
     JNIEnv* env = JSC::Bindings::getJNIEnv();
-    env->CallVoidMethod(m_javaGlue.object(env).get(),
-            m_javaGlue.m_sendMoveMouseIfLatest, clearTextEntry, stopPaintingCaret);
+    AutoJObject javaObject = m_javaGlue.object(env);
+    if (!javaObject.get())
+        return;
+    env->CallVoidMethod(javaObject.get(), m_javaGlue.m_sendMoveMouseIfLatest, clearTextEntry, stopPaintingCaret);
     checkException(env);
 }
 
-void sendMotionUp(
-    WebCore::Frame* framePtr, WebCore::Node* nodePtr, int x, int y)
+void sendMotionUp(WebCore::Frame* framePtr, WebCore::Node* nodePtr, int x, int y)
 {
-    m_viewImpl->m_touchGeneration = ++m_generation;
-    DBG_NAV_LOGD("m_generation=%d framePtr=%p nodePtr=%p x=%d y=%d",
-        m_generation, framePtr, nodePtr, x, y);
+    DBG_NAV_LOGD("m_generation=%d framePtr=%p nodePtr=%p x=%d y=%d", m_generation, framePtr, nodePtr, x, y);
     LOG_ASSERT(m_javaGlue.m_obj, "A WebView was not associated with this WebViewNative!");
+
     JNIEnv* env = JSC::Bindings::getJNIEnv();
-    env->CallVoidMethod(m_javaGlue.object(env).get(), m_javaGlue.m_sendMotionUp,
-        m_generation, (jint) framePtr, (jint) nodePtr, x, y);
+    AutoJObject javaObject = m_javaGlue.object(env);
+    if (!javaObject.get())
+        return;
+    m_viewImpl->m_touchGeneration = ++m_generation;
+    env->CallVoidMethod(javaObject.get(), m_javaGlue.m_sendMotionUp, m_generation, (jint) framePtr, (jint) nodePtr, x, y);
     checkException(env);
 }
 
@@ -1285,8 +1307,10 @@ bool scrollBy(int dx, int dy)
     LOG_ASSERT(m_javaGlue.m_obj, "A java object was not associated with this native WebView!");
 
     JNIEnv* env = JSC::Bindings::getJNIEnv();
-    bool result = env->CallBooleanMethod(m_javaGlue.object(env).get(),
-        m_javaGlue.m_scrollBy, dx, dy, true);
+    AutoJObject javaObject = m_javaGlue.object(env);
+    if (!javaObject.get())
+        return false;
+    bool result = env->CallBooleanMethod(javaObject.get(), m_javaGlue.m_scrollBy, dx, dy, true);
     checkException(env);
     return result;
 }
@@ -1322,29 +1346,40 @@ bool hasFocusNode()
 void rebuildWebTextView()
 {
     JNIEnv* env = JSC::Bindings::getJNIEnv();
-    env->CallVoidMethod(m_javaGlue.object(env).get(),
-            m_javaGlue.m_rebuildWebTextView);
+    AutoJObject javaObject = m_javaGlue.object(env);
+    if (!javaObject.get())
+        return;
+    env->CallVoidMethod(javaObject.get(), m_javaGlue.m_rebuildWebTextView);
     checkException(env);
 }
 
 void viewInvalidate()
 {
     JNIEnv* env = JSC::Bindings::getJNIEnv();
-    env->CallVoidMethod(m_javaGlue.object(env).get(), m_javaGlue.m_viewInvalidate);
+    AutoJObject javaObject = m_javaGlue.object(env);
+    if (!javaObject.get())
+        return;
+    env->CallVoidMethod(javaObject.get(), m_javaGlue.m_viewInvalidate);
     checkException(env);
 }
 
 void viewInvalidateRect(int l, int t, int r, int b)
 {
     JNIEnv* env = JSC::Bindings::getJNIEnv();
-    env->CallVoidMethod(m_javaGlue.object(env).get(), m_javaGlue.m_viewInvalidateRect, l, r, t, b);
+    AutoJObject javaObject = m_javaGlue.object(env);
+    if (!javaObject.get())
+        return;
+    env->CallVoidMethod(javaObject.get(), m_javaGlue.m_viewInvalidateRect, l, r, t, b);
     checkException(env);
 }
 
 void postInvalidateDelayed(int64_t delay, const WebCore::IntRect& bounds)
 {
     JNIEnv* env = JSC::Bindings::getJNIEnv();
-    env->CallVoidMethod(m_javaGlue.object(env).get(), m_javaGlue.m_postInvalidateDelayed,
+    AutoJObject javaObject = m_javaGlue.object(env);
+    if (!javaObject.get())
+        return;
+    env->CallVoidMethod(javaObject.get(), m_javaGlue.m_postInvalidateDelayed,
         delay, bounds.x(), bounds.y(), bounds.maxX(), bounds.maxY());
     checkException(env);
 }
@@ -1352,8 +1387,10 @@ void postInvalidateDelayed(int64_t delay, const WebCore::IntRect& bounds)
 bool inFullScreenMode()
 {
     JNIEnv* env = JSC::Bindings::getJNIEnv();
-    jboolean result = env->CallBooleanMethod(m_javaGlue.object(env).get(),
-            m_javaGlue.m_inFullScreenMode);
+    AutoJObject javaObject = m_javaGlue.object(env);
+    if (!javaObject.get())
+        return false;
+    jboolean result = env->CallBooleanMethod(javaObject.get(), m_javaGlue.m_inFullScreenMode);
     checkException(env);
     return result;
 }