Throttle rendering pipeline for invisible iframes

public/web/WebWidget.h

Index: public/web/WebWidget.h
diff --git a/public/web/WebWidget.h b/public/web/WebWidget.h
index 0b926bb9aad588c3b3fdf061d2061ba6069bd9aa..5535e111b0e5fd68b51b26cc0d71b944b2cd3cce 100644
--- a/public/web/WebWidget.h
+++ b/public/web/WebWidget.h
@@ -110,6 +110,8 @@ public:
 
     virtual void paintCompositedDeprecated(WebCanvas*, const WebRect&) { }
 
+    virtual void didCommitCompositorFrame() { }

[dglazkov, 2015/09/02 21:12:06]

Can you help me understand why this needs to be at the DidComitCompositorFrame
phase and not at the end of WebViewImpl::layout, like
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

[ojan, 2015/09/02 21:17:11]

See
https://codereview.chromium.org/1246173002/diff/520001/Source/web/WebViewImpl....

TL;DR: We do the actual paint recording after WebViewImpl::layout. We compute
the visibility at the end of layout, but we don't want it to apply mid-way
through the pipeline, we want to it apply after the current frame ends and
before the next one begins. Otherwise, we end up painting a frame that's in an
invalid state.

+
     // Run layout and paint of all pending document changes asynchronously.
     // The caller is resposible for keeping the WebLayoutAndPaintAsyncCallback
     // object alive until it is called.