Remove WebLayerTreeView::finishAllRendering(), nothing uses it.

Review URL: https://codereview.chromium.org/1310713006

git-svn-id: svn://svn.chromium.org/blink/trunk@201768 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/public/platform/WebLayerTreeView.h

@@ -128,10 +128,6 @@ public:
     // object alive until it is called.
     virtual void compositeAndReadbackAsync(WebCompositeAndReadbackAsyncCallback*) { }
 
-    // Blocks until the most recently composited frame has finished rendering on the GPU.
-    // This can have a significant performance impact and should be used with care.
-    virtual void finishAllRendering() { }
-
     // Prevents updates to layer tree from becoming visible.
     virtual void setDeferCommits(bool deferCommits) { }