Adds DevTools commands for forced viewport override.

third_party/WebKit/Source/web/ChromeClientImpl.cpp

Index: third_party/WebKit/Source/web/ChromeClientImpl.cpp
diff --git a/third_party/WebKit/Source/web/ChromeClientImpl.cpp b/third_party/WebKit/Source/web/ChromeClientImpl.cpp
index 1c2e7784d2bde4cddf3a0c06d41c1d99231a2e2a..074a1387027f6b5673c465439c32f28d6b1e7e28 100644
--- a/third_party/WebKit/Source/web/ChromeClientImpl.cpp
+++ b/third_party/WebKit/Source/web/ChromeClientImpl.cpp
@@ -605,6 +605,11 @@ void ChromeClientImpl::pageScaleFactorChanged() const
     m_webView->pageScaleFactorChanged();
 }
 
+void ChromeClientImpl::mainFrameScrollOffsetChanged() const
+{
+    m_webView->mainFrameScrollOffsetChanged();
+}
+
 float ChromeClientImpl::clampPageScaleFactorToLimits(float scale) const
 {
     return m_webView->clampPageScaleFactorToLimits(scale);