Defer preferred size updates to after commit

https://crrev.com/581383 removed a preferred size timer and started
synchronously updating preferred sizes in DidUpdateMainFrameLayout.
This caused a performance regression because, even though layout is
up-to-date, the preferred contents size may need to be re-computed.
Script can cause many layouts per frame which was a performance
regression because many multiple preferred contents size updates are now
occurring per frame.

This patch adds a bool for if a layout occurred which may have changed
the preferred content size, and defers the update until after the
commit.

Bug: 872599
Change-Id: Idfe1ba523b1ecfdf8f959bafc2e20ef6a52487bb
Reviewed-on: https://chromium-review.googlesource.com/1172059
Commit-Queue: Philip Rogers <pdr@chromium.org>
Reviewed-by: vmpstr <vmpstr@chromium.org>
Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582708}

android_webview/renderer/aw_render_view_ext.cc

@@ -26,7 +26,8 @@ void AwRenderViewExt::DidCommitCompositorFrame() {
 }
 
 void AwRenderViewExt::DidUpdateMainFrameLayout() {
-  UpdateContentsSize();
+  // The size may have changed.
+  needs_contents_size_update_ = true;
 }
 
 void AwRenderViewExt::OnDestruct() {
@@ -47,6 +48,10 @@ void AwRenderViewExt::UpdateContentsSize() {
   if (!webview || !main_render_frame)
     return;
 
+  if (!needs_contents_size_update_)
+    return;
+  needs_contents_size_update_ = false;
+
   gfx::Size contents_size = main_render_frame->GetWebFrame()->DocumentSize();
 
   // Fall back to contentsPreferredMinimumSize if the mainFrame is reporting a

android_webview/renderer/aw_render_view_ext.h

@@ -31,6 +31,10 @@ class AwRenderViewExt : public content::RenderViewObserver {
 
   gfx::Size last_sent_contents_size_;
 
+  // Whether the contents size may have changed and |UpdateContentsSize| needs
+  // to be called.
+  bool needs_contents_size_update_ = true;
+
   DISALLOW_COPY_AND_ASSIGN(AwRenderViewExt);
 };
 

content/renderer/render_view_impl.cc

@@ -1135,6 +1135,7 @@ GURL RenderViewImpl::GetURLForGraphicsContext3DForWidget() {
 void RenderViewImpl::DidCommitCompositorFrameForWidget() {
   for (auto& observer : observers_)
     observer.DidCommitCompositorFrame();
+  UpdatePreferredSize();
 }
 
 void RenderViewImpl::DidCompletePageScaleAnimationForWidget() {
@@ -1666,7 +1667,8 @@ void RenderViewImpl::DidUpdateMainFrameLayout() {
   for (auto& observer : observers_)
     observer.DidUpdateMainFrameLayout();
 
-  UpdatePreferredSize();
+  // The main frame may have changed size.
+  needs_preferred_size_update_ = true;
 }
 
 void RenderViewImpl::NavigateBackForwardSoon(int offset) {
@@ -1739,6 +1741,11 @@ void RenderViewImpl::UpdatePreferredSize() {
   // message.
   if (!send_preferred_size_changes_ || !webview())
     return;
+
+  if (!needs_preferred_size_update_)
+    return;
+  needs_preferred_size_update_ = false;
+
   blink::WebSize tmp_size = webview()->ContentsPreferredMinimumSize();
   blink::WebRect tmp_rect(0, 0, tmp_size.width, tmp_size.height);
   WidgetClient()->ConvertViewportToWindow(&tmp_rect);
@@ -1853,6 +1860,8 @@ void RenderViewImpl::OnEnablePreferredSizeChangedMode() {
   if (!webview())
     return;
 
+  needs_preferred_size_update_ = true;
+
   // We need to ensure |UpdatePreferredSize| gets called. If a layout is needed,
   // force an update here which will call |DidUpdateMainFrameLayout|.
   webview()->UpdateLifecycle(WebWidget::LifecycleUpdate::kLayout);

content/renderer/render_view_impl.h

@@ -553,6 +553,10 @@ class CONTENT_EXPORT RenderViewImpl : private RenderWidget,
   // If true, we send IPC messages when |preferred_size_| changes.
   bool send_preferred_size_changes_ = false;
 
+  // Whether the preferred size may have changed and |UpdatePreferredSize| needs
+  // to be called.
+  bool needs_preferred_size_update_ = true;
+
   // If non-empty, and |send_preferred_size_changes_| is true, disable drawing
   // scroll bars on windows smaller than this size.  Used for windows that the
   // browser resizes to the size of the content, such as browser action popups.