Allow frames with overflow:hidden scroll in slow scrolling path when scaled up

Source/WebKit/chromium/tests/WebFrameTest.cpp

Index: Source/WebKit/chromium/tests/WebFrameTest.cpp
diff --git a/Source/WebKit/chromium/tests/WebFrameTest.cpp b/Source/WebKit/chromium/tests/WebFrameTest.cpp
index 0e1b4de722a4b1ca59effa82db42f592d35211f5..c1a8d9e72ad9add67b81ed3891022bd8bb5bc3c4 100644
--- a/Source/WebKit/chromium/tests/WebFrameTest.cpp
+++ b/Source/WebKit/chromium/tests/WebFrameTest.cpp
@@ -2999,5 +2999,41 @@ TEST_F(WebFrameTest, CompositorScrollIsUserScrollShortPage)
     m_webView = 0;
 }
 
+TEST_F(WebFrameTest, OverflowHiddenScrollable)
+{
+    WebCore::Settings::setMockScrollbarsEnabled(true);
+    WebCore::Settings::setUsesOverlayScrollbars(true);
+    EXPECT_TRUE(WebCore::ScrollbarTheme::theme()->usesOverlayScrollbars());
+
+    registerMockedHttpURLLoad("clipped-body.html");
+
+    FixedLayoutTestWebViewClient client;
+    client.m_screenInfo.deviceScaleFactor = 1;
+    int fixedLayoutWidth = 500; // Smaller than the full content width 1000. "overflow-x: hidden" will clip in this direction.
+    int fixedLayoutHeight = 3000; // Bigger than the full content height 1000 which won't be clipped.
+
+    m_webView = FrameTestHelpers::createWebViewAndLoad(m_baseURL + "clipped-body.html", true, 0, &client);
+    m_webView->enableFixedLayoutMode(true);
+    m_webView->settings()->setViewportEnabled(true);
+    m_webView->resize(WebSize(fixedLayoutWidth, fixedLayoutHeight));
+    m_webView->layout();
+
+    WebViewImpl* webViewImpl = static_cast<WebViewImpl*>(m_webView);
+    WebCore::FrameView* frameView = webViewImpl->mainFrameImpl()->frameView();
+    m_webView->setFixedLayoutSize(WebSize(fixedLayoutWidth, fixedLayoutHeight));
+    m_webView->layout();
+
+    EXPECT_EQ(fixedLayoutWidth, frameView->contentsWidth());
+    EXPECT_EQ(fixedLayoutWidth, frameView->visibleWidth());
+    EXPECT_FALSE(frameView->isScrollable());
+
+    m_webView->setPageScaleFactorPreservingScrollOffset(2);
+    m_webView->layout();
+
+    EXPECT_EQ(fixedLayoutWidth / 2, frameView->visibleWidth());
+    EXPECT_EQ(fixedLayoutWidth, frameView->contentsWidth());
+    EXPECT_TRUE(frameView->isScrollable());
+    EXPECT_EQ(fixedLayoutWidth / 2, frameView->maximumScrollPosition().x());
+}
 
 } // namespace