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

1 files changed, 3 insertions, 0 deletions

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;