suppress partial screen updates if a canvas element is visible

A PictureSet contains a list of pictures. Each picture draws
part of the screen. If the picture contains a Canvas element,
the corresponding bitmap is not shared.

Small partial invalidates can create a dozen or so pictures,
each of which may be quite small, a few hundred bytes. But
the bitmap referenced by the picture may be large, several
meg.

The backing bitmap is unique to the Canvas element. Since
a canvas rarely benefits from small updates, disable the
partial invalidates if CacheBuilder detects a canvas.

Change-Id: I5761667db3d037d7363dcb01f8a26f7f62e2eabc
http://b/2678787

3 files changed, 8 insertions, 0 deletions

diff --git a/WebKit/android/jni/WebViewCore.cpp b/WebKit/android/jni/WebViewCore.cpp
index 2efd074..beb38cd 100644
--- a/WebKit/android/jni/WebViewCore.cpp
+++ b/WebKit/android/jni/WebViewCore.cpp
@@ -590,6 +590,9 @@ void WebViewCore::recordPictureSet(PictureSet* content)
         height = view->contentsHeight();
     }
 
+    if (cacheBuilder().pictureSetDisabled())
+        content->clear();
+
     content->checkDimensions(width, height, &m_addInval);
 
     // The inval region may replace existing pictures. The existing pictures
diff --git a/WebKit/android/nav/CacheBuilder.cpp b/WebKit/android/nav/CacheBuilder.cpp
index 09e5e59..c343fa0 100644
--- a/WebKit/android/nav/CacheBuilder.cpp
+++ b/WebKit/android/nav/CacheBuilder.cpp
@@ -867,6 +867,7 @@ bool CacheBuilder::AnyIsClick(Node* node)
 void CacheBuilder::buildCache(CachedRoot* root)
 {
     Frame* frame = FrameAnd(this);
+    mPictureSetDisabled = false;
     BuildFrame(frame, frame, root, (CachedFrame*) root);
     root->finishInit(); // set up frame parent pointers, child pointers
     setData((CachedFrame*) root);
@@ -1131,6 +1132,8 @@ void CacheBuilder::BuildFrame(Frame* root, Frame* frame,
 
         if (node->hasTagName(HTMLNames::bodyTag))
             bodyPos = originalAbsBounds.location();
+        else if (node->hasTagName(HTMLNames::canvasTag))
+            mPictureSetDisabled = true;
         if (checkForPluginViewThatWantsFocus(nodeRenderer)) {
             bounds = absBounds;
             isUnclipped = true;
diff --git a/WebKit/android/nav/CacheBuilder.h b/WebKit/android/nav/CacheBuilder.h
index 4ded58d..8183954 100644
--- a/WebKit/android/nav/CacheBuilder.h
+++ b/WebKit/android/nav/CacheBuilder.h
@@ -94,6 +94,7 @@ public:
     static IntRect getAreaRect(const HTMLAreaElement* area);
     static void GetGlobalOffset(Frame* , int* x, int * y);
     static void GetGlobalOffset(Node* , int* x, int * y);
+    bool pictureSetDisabled() { return mPictureSetDisabled; }
     static bool validNode(Frame* startFrame, void* framePtr, void* nodePtr);
 private:
     enum AddressProgress {
@@ -249,6 +250,7 @@ private:
     Node* tryFocus(Direction direction);
     Node* trySegment(Direction direction, int mainStart, int mainEnd);
     CachedNodeBits mAllowableTypes;
+    bool mPictureSetDisabled;
 #if DUMP_NAV_CACHE
 public:
     class Debug {