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

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/frame/FrameView.h"
 
 #include "bindings/core/v8/ExceptionStatePlaceholder.h"
 #include "core/frame/Settings.h"
 #include "core/html/HTMLElement.h"
 #include "core/layout/LayoutObject.h"
@@ skipping 149 matching lines @@
 // performance. See crbug.com/586852 for details.
 TEST_P(FrameViewTest, HideTooltipWhenScrollPositionChanges)
 {
     document().body()->setInnerHTML("<div style='width:1000px;height:1000px'></div>", ASSERT_NO_EXCEPTION);
     document().view()->updateAllLifecyclePhases();
 
     EXPECT_CALL(chromeClient(), setToolTip(String(), _));
     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