Expose an API for throttling nsRefreshDriver. Contributes to JB#30183

In sailfish-browser we're interested in being able to limit view CPU
usage while still keeping it active. Browser live covers are prime user
of such feature. This patch makes it possible to enable layout engine's
refresh driver throttling without fully deactivating the view. When
refresh driver throttling is enabled the engine will update/repaint the
content less often. The frequeency can be tweaked through
layout.throttled_frame_rate pref (defaults to 1).

embedding/embedlite/EmbedLiteView.cpp

@@ -94,6 +94,14 @@ EmbedLiteView::SetIsFocused(bool aIsFocused)
   unused << mViewParent->SendSetIsFocused(aIsFocused);
 }
 
+void
+EmbedLiteView::SetThrottlePainting(bool aThrottle)
+{
+  LOGT();
+  NS_ENSURE_TRUE(mViewParent, );
+  unused << mViewParent->SendSetThrottlePainting(aThrottle);
+}
+
 void
 EmbedLiteView::SuspendTimeouts()
 {

embedding/embedlite/EmbedLiteView.h

@@ -90,6 +90,7 @@ class EmbedLiteView
   virtual void LoadURL(const char* aUrl);
   virtual void SetIsActive(bool);
   virtual void SetIsFocused(bool);
+  virtual void SetThrottlePainting(bool);
   virtual void SuspendTimeouts();
   virtual void ResumeTimeouts();
   virtual void GoBack();

embedding/embedlite/PEmbedLiteView.ipdl

@@ -40,6 +40,7 @@ child:
     SetGLViewSize(gfxSize aSize);
     SetIsActive(bool aIsActive);
     SetIsFocused(bool aIsFocused);
+    SetThrottlePainting(bool aThrottle);
     SuspendTimeouts();
     ResumeTimeouts();
     AsyncScrollDOMEvent(gfxRect contentRect, gfxSize scrollSize);

embedding/embedlite/embedshared/EmbedLiteViewBaseChild.cpp

@@ -20,7 +20,7 @@
 #include "nsIFocusManager.h"
 #include "nsFocusManager.h"
 #include "nsIWebBrowserChrome.h"
-
+#include "nsRefreshDriver.h"
 #include "nsIDOMWindowUtils.h"
 #include "nsPIDOMWindow.h"
 #include "nsIDocument.h"
@@ -511,6 +511,14 @@ EmbedLiteViewBaseChild::RecvSetIsFocused(const bool& aIsFocused)
   return true;
 }
 
+bool
+EmbedLiteViewBaseChild::RecvSetThrottlePainting(const bool& aThrottle)
+{
+  LOGT("aThrottle:%d", aThrottle);
+  mHelper->GetPresContext()->RefreshDriver()->SetThrottled(aThrottle);
+  return true;
+}
+
 bool
 EmbedLiteViewBaseChild::RecvSuspendTimeouts()
 {

embedding/embedlite/embedshared/EmbedLiteViewBaseChild.h

@@ -118,6 +118,7 @@ class EmbedLiteViewBaseChild : public PEmbedLiteViewChild,
 
   virtual bool RecvSetIsActive(const bool&) override;
   virtual bool RecvSetIsFocused(const bool&) override;
+  virtual bool RecvSetThrottlePainting(const bool&) override;
   virtual bool RecvSuspendTimeouts() override;
   virtual bool RecvResumeTimeouts() override;
   virtual bool RecvLoadFrameScript(const nsString&) override;