Merge 116587 - [chromium] Don't draw when canDraw() is false

Source/WebCore/ChangeLog

Index: Source/WebCore/ChangeLog
===================================================================
--- Source/WebCore/ChangeLog	(revision 117086)
+++ Source/WebCore/ChangeLog	(working copy)
@@ -1,3 +1,35 @@
+2012-05-09  Dana Jansens  <danakj@chromium.org>
+
+        [chromium] Don't draw when canDraw() is false
+        https://bugs.webkit.org/show_bug.cgi?id=85829
+
+        Reviewed by Adrienne Walker.
+
+        This is based on the work of Daniel Sievers in bug
+        https://bugs.webkit.org/show_bug.cgi?id=82680. When canDraw() is false,
+        we should not call drawLayers() or prepareToDraw() in both Single- and
+        Multi-Threaded mode.
+
+        drawLayers() is crashing in single threaded mode, and this attempts to
+        prevent it from being called with invalid state. While making it behave
+        properly in single-threaded mode, it seems appropriate to unrevert the
+        parts of 82680 that made threaded mode behave similarly appropriately.
+
+        A single-threaded test is not included since LTHTests is unable to run
+        in single-threaded mode at this time (pending work from Ian Vollick). So
+        we test in threaded mode only with a note to include a single thread
+        version.
+
+        Tests: CCLayerTreeHostTestCanDrawBlocksDrawing.runMultiThread
+
+        * platform/graphics/chromium/cc/CCLayerTreeHostImpl.cpp:
+        (WebCore::CCLayerTreeHostImpl::prepareToDraw):
+        (WebCore::CCLayerTreeHostImpl::drawLayers):
+        * platform/graphics/chromium/cc/CCSingleThreadProxy.cpp:
+        (WebCore::CCSingleThreadProxy::doComposite):
+        * platform/graphics/chromium/cc/CCThreadProxy.cpp:
+        (WebCore::CCThreadProxy::scheduledActionDrawAndSwapInternal):
+
 2012-05-08  Dana Jansens  <danakj@chromium.org>
 
         [chromium] Reflections with masks should not occlude