Test that FrameView::incrementVisuallyNonEmptyPixelCount() doesn't overflow

third_party/WebKit/Source/core/frame/FrameViewTest.cpp

Index: third_party/WebKit/Source/core/frame/FrameViewTest.cpp
diff --git a/third_party/WebKit/Source/core/frame/FrameViewTest.cpp b/third_party/WebKit/Source/core/frame/FrameViewTest.cpp
index 5438ffa3f6faa0fd4d4b988dacfb5034e893a72a..c9e61146d518e021386e43f3c2501fd14544c660 100644
--- a/third_party/WebKit/Source/core/frame/FrameViewTest.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameViewTest.cpp
@@ -167,5 +167,12 @@ TEST_P(FrameViewTest, HideTooltipWhenScrollPositionChanges)
     document().view()->layoutViewportScrollableArea()->setScrollPosition(DoublePoint(1, 1), UserScroll);
 }
 
+TEST_P(FrameViewTest, NoOverflowInIncrementVisuallyNonEmptyPixelCount)
+{
+    EXPECT_FALSE(document().view()->isVisuallyNonEmpty());
+    document().view()->incrementVisuallyNonEmptyPixelCount(IntSize(2147483647, 2147483647));

[bokan, 2016/08/09 14:10:32]

This won't actually fail unless run on the sanitizer though, right? Perhaps come
up with numbers that, when overflowing, end up less than the
visualPixelThreshold in incrementVisuallyNonEmptyPixelCount?

[hiroshige, 2016/08/12 06:30:16]

2147483647 * 2147483647 would become 4 if calculated in 32-bit, so this test
would fail.

However I changed the size to 65536 * 65536 (which clearly would become 0 in
32-bit), partially because there is a limit on sizes of SVGs and we cannot test
a SVG file with 2147483647 * 2147483647 pixels.

+    EXPECT_TRUE(document().view()->isVisuallyNonEmpty());
+}
+
 } // namespace
 } // namespace blink