[DevTools] Use device metrics emulation implemented in content.

public/web/WebView.h

Index: public/web/WebView.h
diff --git a/public/web/WebView.h b/public/web/WebView.h
index a9457988aaf0eed8f7a9bc4d541cd11eb5b01525..9a97cbb78c48f0279bcd03953e6ff830fc7fa401 100644
--- a/public/web/WebView.h
+++ b/public/web/WebView.h
@@ -400,6 +400,10 @@ public:
                                   WebString* value) const = 0;
     virtual void setInspectorSetting(const WebString& key,
                                      const WebString& value) = 0;
+    virtual void setDeviceEmulationParameters(

[aelias_OOO_until_Jul13, 2013/10/01 08:08:51]

You're introducing a second Blink API to bounce back some information that Blink
could've computed in the first place.  Let's avoid this criss-crossing
dependency.

The new information you're getting back through here is the rootLayerScale which
is calculated by fit_to_view.  But you have enough information to do the
fit_to_view calculation on the Blink side.  Please move that calculation to
Blink and then tell both RenderView and WebViewImpl about the scale you
calculated, and delete this WebView.h change.

[aelias_OOO_until_Jul13, 2013/10/01 08:24:22]

As discussed offline, it can't be eliminated, so let's just split into two
narrowly named methods for clarity:

setCompositorDeviceScaleFactorOverride()
setRootLayerScaleTransform()

[dgozman, 2013/10/01 15:26:34]

Done.

+        bool enabled,
+        float deviceScaleFactor,
+        float rootLayerScale) = 0;
 
     // The embedder may optionally engage a WebDevToolsAgent.  This may only
     // be set once per WebView.