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 47dc1fbf2292106d213928f9ca31439b71e48397..5387e55ae5795d470a7e174068a048618f446a48 100644
--- a/third_party/WebKit/Source/web/ChromeClientImpl.cpp
+++ b/third_party/WebKit/Source/web/ChromeClientImpl.cpp
@@ -606,6 +606,11 @@ 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);