Disabled pinch zooming in non-browser Aura windows.

ui/web_dialogs/web_dialog_web_contents_delegate.cc

Index: ui/web_dialogs/web_dialog_web_contents_delegate.cc
diff --git a/ui/web_dialogs/web_dialog_web_contents_delegate.cc b/ui/web_dialogs/web_dialog_web_contents_delegate.cc
index 4a3f0dff2dfd01e62a0f37aa86d10cc626702959..ea0006ae79d8e9a20db3fc543db5fdc7faa98ddc 100644
--- a/ui/web_dialogs/web_dialog_web_contents_delegate.cc
+++ b/ui/web_dialogs/web_dialog_web_contents_delegate.cc
@@ -6,6 +6,7 @@
 
 #include "base/logging.h"
 #include "content/public/browser/web_contents.h"
+#include "third_party/WebKit/public/web/WebInputEvent.h"
 
 using content::BrowserContext;
 using content::OpenURLParams;
@@ -55,4 +56,13 @@ bool WebDialogWebContentsDelegate::IsPopupOrPanel(
   return true;
 }
 
+bool WebDialogWebContentsDelegate::PreHandleGestureEvent(
+    WebContents* source,
+    const blink::WebGestureEvent& event) {
+  // Disable pinch zooming.
+  return event.type == blink::WebGestureEvent::GesturePinchBegin ||
+      event.type == blink::WebGestureEvent::GesturePinchUpdate ||
+      event.type == blink::WebGestureEvent::GesturePinchEnd;
+}
+
 }  // namespace ui