Avoid passing uninitialized value to markRectAsNonOpaque.

Source/platform/graphics/GraphicsContextTest.cpp

Index: Source/platform/graphics/GraphicsContextTest.cpp
diff --git a/Source/platform/graphics/GraphicsContextTest.cpp b/Source/platform/graphics/GraphicsContextTest.cpp
index fd4a9588621b018e68224fc9756d57c97ef4e61d..3b8b330631bab15276ec5862d2b2bb16b35a5393 100644
--- a/Source/platform/graphics/GraphicsContextTest.cpp
+++ b/Source/platform/graphics/GraphicsContextTest.cpp
@@ -1042,6 +1042,59 @@ TEST(GraphicsContextTest, PreserveOpaqueOnlyMattersForFirstLayer)
     EXPECT_PIXELS_MATCH_EXACT(bitmap, context.opaqueRegion().asRect());
 }
 
+TEST(GraphicsContextTest, OpaqueRegionForLayer)
+{
+    // Set non-rect device clip.
+    Path path;
+    path.moveTo(FloatPoint(0, 0));
+    path.addLineTo(FloatPoint(50, 50));
+
+    SkCanvas canvas(50, 50);

[danakj, 2014/08/05 13:53:28]

can you make the canvas bigger than the path's bounding box, or make the path
smaller than the canvas?

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

Done.

+    GraphicsContext context(&canvas);
+    context.clipPath(path, RULE_EVENODD);
+    context.setRegionTrackingMode(GraphicsContext::RegionTrackingOpaque);
+
+    Color opaque(1.0f, 0.0f, 0.0f, 1.0f);
+
+    // Set Opaque Rect.

[danakj, 2014/08/05 13:53:28]

Say why not what, all of these comments just say what the code is doing. Instead
they should explain why they are doing what they are doing.

[sohanjg, 2014/08/05 15:23:20]

Done.

+    context.fillRect(FloatRect(30, 30, 90, 90), opaque, CompositeSourceOver);

[danakj, 2014/08/05 13:53:28]

isn't this outside the bounds of the canvas?

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

Done.
I was trying to avoid markRectAsNonOpaque early-outs and get a opaque region,
but that's not imp in this test i gess.

+    // Begin non-opaque-preserving layer.
+    context.setCompositeOperation(CompositeSourceOut);
+    context.beginTransparencyLayer(0.5);
+
+    context.endLayer();
+    EXPECT_EQ_RECT(IntRect(), context.opaqueRegion().asRect());
+
+    // Set rect device clip.
+    SkBitmap bitmap;
+    ASSERT_TRUE(bitmap.allocN32Pixels(50, 50));
+    bitmap.eraseColor(0);
+    SkCanvas canvas2(bitmap);
+
+    GraphicsContext context2(&canvas2);
+    context2.setRegionTrackingMode(GraphicsContext::RegionTrackingOpaque);
+
+    // Set Opaque Rect.
+    context2.fillRect(FloatRect(30, 30, 90, 90), opaque, CompositeSourceOver);
+    // Begin non-opaque-preserving layer.
+    context2.setCompositeOperation(CompositeSourceOut);
+    context2.beginTransparencyLayer(0.5);
+
+    context2.endLayer();
+    EXPECT_EQ_RECT(IntRect(), context2.opaqueRegion().asRect());
+    EXPECT_PIXELS_MATCH(bitmap, context2.opaqueRegion().asRect());
+
+    // Set Opaque Rect.
+    context2.fillRect(FloatRect(30, 30, 90, 90), opaque, CompositeSourceOver);
+    // Begin opaque-preserving layer.
+    context2.setCompositeOperation(CompositeSourceOver);
+    context2.beginTransparencyLayer(0.5);
+
+    context2.endLayer();
+    EXPECT_EQ_RECT(IntRect(30, 30, 20, 20), context2.opaqueRegion().asRect());
+    EXPECT_PIXELS_MATCH(bitmap, context2.opaqueRegion().asRect());
+}
+
 #define DISPATCH1(c1, c2, op, param1) do { c1.op(param1); c2.op(param1); } while (0);
 #define DISPATCH2(c1, c2, op, param1, param2) do { c1.op(param1, param2); c2.op(param1, param2); } while (0);