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..dde8fcd56cfc6d3c3bc366e3d52e258694579cff 100644
--- a/Source/platform/graphics/GraphicsContextTest.cpp
+++ b/Source/platform/graphics/GraphicsContextTest.cpp
@@ -1042,6 +1042,66 @@ TEST(GraphicsContextTest, PreserveOpaqueOnlyMattersForFirstLayer)
     EXPECT_PIXELS_MATCH_EXACT(bitmap, context.opaqueRegion().asRect());
 }
 
+TEST(GraphicsContextTest, OpaqueRegionForLayer)
+{
+    // For non-opaque preserving mode and deviceClip is not rect
+    // we will mark opaque rect as empty.
+    Path path;
+    path.moveTo(FloatPoint(0, 0));
+    path.addLineTo(FloatPoint(50, 50));
+
+    SkCanvas canvas(400, 400);
+    GraphicsContext context(&canvas);
+    context.clipPath(path, RULE_EVENODD);
+    context.setRegionTrackingMode(GraphicsContext::RegionTrackingOpaque);
+
+    Color opaque(1.0f, 0.0f, 0.0f, 1.0f);
+
+    context.fillRect(FloatRect(30, 30, 90, 90), opaque, CompositeSourceOver);

[danakj, 2014/08/05 15:26:54]

Can you EXPECT_EQ the opaqueRegion after this, and verify it's not empty so we
see the code below actually doing something?

[sohanjg, 2014/08/06 05:56:21]

Done.

+    context.setCompositeOperation(CompositeSourceOut);
+    context.beginTransparencyLayer(0.5);
+
+    context.endLayer();
+    EXPECT_EQ_RECT(IntRect(), context.opaqueRegion().asRect());
+
+    // For opaque preserving mode and deviceClip is not rect
+    // we will not alter opaque rect.
+    context.fillRect(FloatRect(30, 30, 90, 90), opaque, CompositeSourceOver);
+    context.setCompositeOperation(CompositeSourceOver);
+    context.beginTransparencyLayer(0.5);
+
+    context.endLayer();
+    EXPECT_EQ_RECT(IntRect(), context.opaqueRegion().asRect());
+
+    SkBitmap bitmap;
+    ASSERT_TRUE(bitmap.allocN32Pixels(400, 400));
+    bitmap.eraseColor(0);
+    SkCanvas canvas2(bitmap);
+
+    GraphicsContext context2(&canvas2);
+    context2.setRegionTrackingMode(GraphicsContext::RegionTrackingOpaque);
+
+    // For non-opaque preserving mode and deviceClip is rect
+    // we will mark device clip rect as non opaque.
+    context2.fillRect(FloatRect(30, 30, 90, 90), opaque, CompositeSourceOver);

[danakj, 2014/08/05 15:26:54]

Can you EXPECT_EQ the opaqueRegion after this, and verify it's not empty so we
see the code below actually doing something?

Also how does this part differ from the above other than using a bitmap? Do we
need both or is just this one enough?

[sohanjg, 2014/08/05 16:48:12]

this part has device clip as 'rect', we would need to test that too, right ? or
it can be ignored ?

[danakj, 2014/08/05 17:18:34]

Oh, this is a different context, i missed that "2". Can you split this into a
separate test case?

[sohanjg, 2014/08/06 05:56:21]

Done.

+    context2.setCompositeOperation(CompositeSourceOut);
+    context2.beginTransparencyLayer(0.5);
+
+    context2.endLayer();
+    EXPECT_EQ_RECT(IntRect(), context2.opaqueRegion().asRect());
+    EXPECT_PIXELS_MATCH(bitmap, context2.opaqueRegion().asRect());
+
+    // For opaque preserving mode and deviceClip is rect
+    // we will intersect device clip rect with src opaque rect.
+    context2.fillRect(FloatRect(30, 30, 90, 90), opaque, CompositeSourceOver);
+    context2.setCompositeOperation(CompositeSourceOver);
+    context2.beginTransparencyLayer(0.5);
+
+    context2.endLayer();
+    EXPECT_EQ_RECT(IntRect(30, 30, 90, 90), 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);