Bug 1482109 - Use the generic memory pressure observer in PuppetWidget. r=sotaro

widget/PuppetWidget.cpp

@@ -139,11 +139,7 @@ PuppetWidget::InfallibleCreate(nsIWidget* aParent,
   else {
     Resize(mBounds.X(), mBounds.Y(), mBounds.Width(), mBounds.Height(), false);
   }
-  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
-  if (obs) {
-    mMemoryPressureObserver = new MemoryPressureObserver(this);
-    obs->AddObserver(mMemoryPressureObserver, "memory-pressure", false);
-  }
+  mMemoryPressureObserver = MemoryPressureObserver::Create(this);
 }
 
 nsresult
@@ -193,9 +189,9 @@ PuppetWidget::Destroy()
   Base::Destroy();
   mPaintTask.Revoke();
   if (mMemoryPressureObserver) {
-    mMemoryPressureObserver->Remove();
+    mMemoryPressureObserver->Unregister();
+    mMemoryPressureObserver = nullptr;
   }
-  mMemoryPressureObserver = nullptr;
   mChild = nullptr;
   if (mLayerManager) {
     mLayerManager->Destroy();
@@ -1137,36 +1133,15 @@ PuppetWidget::PaintNowIfNeeded()
   }
 }
 
-NS_IMPL_ISUPPORTS(PuppetWidget::MemoryPressureObserver, nsIObserver)
-
-NS_IMETHODIMP
-PuppetWidget::MemoryPressureObserver::Observe(nsISupports* aSubject,
-                                              const char* aTopic,
-                                              const char16_t* aData)
-{
-  if (!mWidget) {
-    return NS_OK;
-  }
-
-  if (strcmp("memory-pressure", aTopic) == 0 &&
-      !StringBeginsWith(nsDependentString(aData),
-                        NS_LITERAL_STRING("low-memory-ongoing"))) {
-    if (!mWidget->mVisible && mWidget->mLayerManager &&
-        XRE_IsContentProcess()) {
-      mWidget->mLayerManager->ClearCachedResources();
-    }
-  }
-  return NS_OK;
-}
-
 void
-PuppetWidget::MemoryPressureObserver::Remove()
+PuppetWidget::OnMemoryPressure(layers::MemoryPressureReason aWhy)
 {
-  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
-  if (obs) {
-    obs->RemoveObserver(this, "memory-pressure");
+  if (aWhy != MemoryPressureReason::LOW_MEMORY_ONGOING &&
+      mVisible &&
+      mLayerManager &&
+      XRE_IsContentProcess()) {
+    mLayerManager->ClearCachedResources();
   }
-  mWidget = nullptr;
 }
 
 bool

widget/PuppetWidget.h

@@ -27,6 +27,7 @@
 #include "mozilla/ContentCache.h"
 #include "mozilla/EventForwards.h"
 #include "mozilla/TextEventDispatcherListener.h"
+#include "mozilla/layers/MemoryPressureObserver.h"
 
 namespace mozilla {
 
@@ -40,6 +41,7 @@ struct AutoCacheNativeKeyCommands;
 
 class PuppetWidget : public nsBaseWidget
                    , public TextEventDispatcherListener
+                   , public layers::MemoryPressureListener
 {
   typedef mozilla::CSSRect CSSRect;
   typedef mozilla::dom::TabChild TabChild;
@@ -322,6 +324,7 @@ public:
                       uint32_t aIndexOfKeypress,
                       void* aData) override;
 
+  virtual void OnMemoryPressure(layers::MemoryPressureReason aWhy) override;
 private:
   nsresult Paint();
 
@@ -358,18 +361,6 @@ private:
     PuppetWidget* mWidget;
   };
 
-  class MemoryPressureObserver : public nsIObserver {
-  public:
-    NS_DECL_ISUPPORTS
-    NS_DECL_NSIOBSERVER
-    explicit MemoryPressureObserver(PuppetWidget* aWidget) : mWidget(aWidget) {}
-    void Remove();
-  private:
-    virtual ~MemoryPressureObserver() {}
-    PuppetWidget* mWidget;
-  };
-  friend class MemoryPressureObserver;
-
   // TabChild normally holds a strong reference to this PuppetWidget
   // or its root ancestor, but each PuppetWidget also needs a
   // reference back to TabChild (e.g. to delegate nsIWidget IME calls
@@ -382,7 +373,7 @@ private:
   RefPtr<PuppetWidget> mChild;
   LayoutDeviceIntRegion mDirtyRegion;
   nsRevocableEventPtr<PaintTask> mPaintTask;
-  RefPtr<MemoryPressureObserver> mMemoryPressureObserver;
+  RefPtr<layers::MemoryPressureObserver> mMemoryPressureObserver;
   // XXX/cjones: keeping this around until we teach LayerManager to do
   // retained-content-only transactions
   RefPtr<DrawTarget> mDrawTarget;