Fix the Java bridge to correctly handle null strings

Passing null to methods expecting java/lang/String ...
- Previously null was converted to the empty string but should be
  converted to Java null.
- convertNPVariantToJavaValue() already converts a null NPVariant to a
  null WTF::String.
- Fixed javaValueToJvalue() to convert a null WTF::String to a null
  jvalue.

Returning null from a method with return type java/lang/String ...
- Previously this would crash when trying to get the characters from
  the null jstring, but should return JavaScript undefined.
- Fixed jvalueToJavaValue() to convert a null jvalue to a null
  WTF::String.
- Fixed convertJavaValueToNPVariant() to convert a null WTF::String to
  a void NPVariant.

Both of these are regressions from HC due to
http://trac.webkit.org/changeset/82194.

Added tests in https://android-git.corp.google.com/g/#/c/132580

Bug: 5222742
Change-Id: Id08bc7b40a51426fa7638ad0ed5260d09f3e28bb

1 files changed, 15 insertions, 0 deletions

diff --git a/Source/WebCore/bridge/jni/v8/JNIUtilityPrivate.cpp b/Source/WebCore/bridge/jni/v8/JNIUtilityPrivate.cpp
index 0d1a9f2..47b88d6 100644
--- a/Source/WebCore/bridge/jni/v8/JNIUtilityPrivate.cpp
+++ b/Source/WebCore/bridge/jni/v8/JNIUtilityPrivate.cpp
@@ -352,6 +352,13 @@ void convertJavaValueToNPVariant(JavaValue value, NPVariant* result)
 
     case JavaTypeString:
         {
+#if PLATFORM(ANDROID)
+            // This entire file will likely be removed usptream soon.
+            if (value.m_stringValue.isNull()) {
+                VOID_TO_NPVARIANT(*result);
+                break;
+            }
+#endif
             const char* utf8String = strdup(value.m_stringValue.utf8().data());
             // The copied string is freed in NPN_ReleaseVariantValue (see npruntime.cpp)
             STRINGZ_TO_NPVARIANT(utf8String, *result);
@@ -429,6 +436,10 @@ JavaValue jvalueToJavaValue(const jvalue& value, const JavaType& type)
     case JavaTypeString:
         {
             jstring javaString = static_cast<jstring>(value.l);
+            if (!javaString) {
+                // result.m_stringValue is null by default
+                break;
+            }
             const UChar* characters = getUCharactersFromJStringInEnv(getJNIEnv(), javaString);
             // We take a copy to allow the Java String to be released.
             result.m_stringValue = String(characters, getJNIEnv()->GetStringLength(javaString));
@@ -487,6 +498,10 @@ jvalue javaValueToJvalue(const JavaValue& value)
         // be released when the call stack returns to Java. Note that this
         // may cause leaks if invoked from a native message loop, as is the
         // case in workers.
+        if (value.m_stringValue.isNull()) {
+            // result.l is null by default.
+            break;
+        }
         result.l = getJNIEnv()->NewString(value.m_stringValue.characters(), value.m_stringValue.length());
         break;
     case JavaTypeBoolean: