Avoid passing uninitialized value to markRectAsNonOpaque.

Source/platform/graphics/RegionTracker.cpp

 /*
  * Copyright (c) 2012, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 155 matching lines @@
     SkColorFilter* colorFilter = paint.getColorFilter();
     if (colorFilter && !(colorFilter->getFlags() & SkColorFilter::kAlphaUnchanged_Flag))
         return false;
     return true;
 }
 
 // Returns true if there is a rectangular clip, with the result in |deviceClipRect|.
 static inline bool getDeviceClipAsRect(const GraphicsContext* context, SkRect& deviceClipRect)
 {
     // Get the current clip in device coordinate space.
-    if (!context->canvas()->isClipRect())
+    if (!context->canvas()->isClipRect()) {
+        deviceClipRect.setEmpty();
         return false;
+    }
 
     SkIRect deviceClipIRect;
     if (context->canvas()->getClipDeviceBounds(&deviceClipIRect))
         deviceClipRect.set(deviceClipIRect);
     else
         deviceClipRect.setEmpty();
 
     return true;
 }
 
@@ skipping 158 matching lines @@
     SkRect deviceClipRect;
     getDeviceClipAsRect(context, deviceClipRect);
     markRectAsNonOpaque(deviceClipRect);
 }
 
 void RegionTracker::applyOpaqueRegionFromLayer(const GraphicsContext* context, const SkRect& layerOpaqueRect, const SkPaint& paint)
 {
     SkRect deviceClipRect;
     bool deviceClipIsARect = getDeviceClipAsRect(context, deviceClipRect);
 
-    if (deviceClipRect.isEmpty())
+    if (deviceClipIsARect && deviceClipRect.isEmpty())
         return;
 
     SkRect sourceOpaqueRect = layerOpaqueRect;
     // Save the opaque area in the destination, so we can preserve the parts of it under the source opaque area if possible.
     SkRect destinationOpaqueRect = currentTrackingOpaqueRect();
 
     bool outsideSourceOpaqueRectPreservesOpaque = xfermodePreservesOpaque(paint, false);
-    if (!outsideSourceOpaqueRectPreservesOpaque)
+    if (!outsideSourceOpaqueRectPreservesOpaque) {
+        if (!deviceClipIsARect) {
+            markAllAsNonOpaque();
+            return;
+        }
         markRectAsNonOpaque(deviceClipRect);
+    }
 
-    if (!deviceClipIsARect)

[danakj, 2014/08/05 13:54:15]

What if !deviceClipIsARect but outsideSourceOpaqueRectPreservesOpaque? We need
this early out in that case still.

[sohanjg, 2014/08/05 15:23:21]

Done.
added a test too.

-        return;
     if (!sourceOpaqueRect.intersect(deviceClipRect))
         return;
 
     bool sourceOpaqueRectDrawsOpaque = paintIsOpaque(paint, FillOnly, 0);
     bool sourceOpaqueRectXfersOpaque = xfermodeIsOpaque(paint, sourceOpaqueRectDrawsOpaque);
     bool sourceOpaqueRectPreservesOpaque = xfermodePreservesOpaque(paint, sourceOpaqueRectDrawsOpaque);
 
     // If the layer's opaque area is being drawn opaque in the layer below, then mark it opaque. Otherwise,
     // if it preserves opaque then keep the intersection of the two.
     if (sourceOpaqueRectXfersOpaque)
@@ skipping 82 matching lines @@
     opaqueRect.setEmpty();
 }
 
 SkRect& RegionTracker::currentTrackingOpaqueRect()
 {
     // If we are drawing into a canvas layer, then track the opaque rect in that layer.
     return m_canvasLayerStack.isEmpty() ? m_opaqueRect : m_canvasLayerStack.last().opaqueRect;
 }
 
 } // namespace blink