Bug 1484173 - Expose the vsync interval via the CompositorVsyncSchedulerOwner interface. r=sotaro

We need this for the next patch.

Differential Revision: https://phabricator.services.mozilla.com/D8765

--HG--
extra : moz-landing-system : lando

gfx/layers/ipc/CompositorBridgeParent.h

@@ -481,7 +481,7 @@ public:
     return mOptions;
   }
 
-  TimeDuration GetVsyncInterval() const {
+  TimeDuration GetVsyncInterval() const override {
     // the variable is called "rate" but really it's an interval
     return mVsyncRate;
   }

gfx/layers/ipc/CompositorVsyncSchedulerOwner.h

@@ -21,6 +21,7 @@ public:
   virtual bool IsPendingComposite() = 0;
   virtual void FinishPendingComposite() = 0;
   virtual void CompositeToTarget(gfx::DrawTarget* aTarget, const gfx::IntRect* aRect = nullptr) = 0;
+  virtual TimeDuration GetVsyncInterval() const = 0;
 };
 
 } // namespace layers

gfx/layers/wr/WebRenderBridgeParent.cpp

@@ -1607,6 +1607,17 @@ WebRenderBridgeParent::CompositeToTarget(gfx::DrawTarget* aTarget, const gfx::In
   MaybeGenerateFrame(/* aForceGenerateFrame */ false);
 }
 
+TimeDuration
+WebRenderBridgeParent::GetVsyncInterval() const
+{
+  // This function should only get called in the root WRBP
+  MOZ_ASSERT(IsRootWebRenderBridgeParent());
+  if (CompositorBridgeParent* cbp = GetRootCompositorBridgeParent()) {
+    return cbp->GetVsyncInterval();
+  }
+  return TimeDuration();
+}
+
 void
 WebRenderBridgeParent::MaybeGenerateFrame(bool aForceGenerateFrame)
 {

gfx/layers/wr/WebRenderBridgeParent.h

@@ -143,6 +143,7 @@ public:
   bool IsPendingComposite() override { return false; }
   void FinishPendingComposite() override { }
   void CompositeToTarget(gfx::DrawTarget* aTarget, const gfx::IntRect* aRect = nullptr) override;
+  TimeDuration GetVsyncInterval() const override;
 
   // CompositableParentManager
   bool IsSameProcess() const override;