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 94 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(), mockSetToolTip(document().frame(), String(), _));
     document().view()->layoutViewportScrollableArea()->setScrollPosition(DoublePoint(1, 1), UserScroll);
 }
 
+// NoOverflowInIncrementVisuallyNonEmptyPixelCount tests fail if the number of
+// pixels is calculated in 32-bit integer, because 65536 * 65536 would become 0
+// if it was calculated in 32-bit and thus it would be considered as empty.
+TEST_P(FrameViewTest, NoOverflowInIncrementVisuallyNonEmptyPixelCount)
+{
+    EXPECT_FALSE(document().view()->isVisuallyNonEmpty());
+    document().view()->incrementVisuallyNonEmptyPixelCount(IntSize(65536, 65536));
+    EXPECT_TRUE(document().view()->isVisuallyNonEmpty());
+}
+
 } // namespace
 } // namespace blink