Bug 757847 - Use a reference rather than a pointer that is never null. r=ajuma

gfx/layers/ipc/CompositorParent.cpp

@@ -347,38 +347,36 @@ CompositorParent::TransformShadowTree()
   ShadowLayer* shadow = layer->AsShadowLayer();
   ContainerLayer* container = layer->AsContainerLayer();
 
-  const FrameMetrics* metrics = &container->GetFrameMetrics();
+  const FrameMetrics& metrics = container->GetFrameMetrics();
   const gfx3DMatrix& rootTransform = mLayerManager->GetRoot()->GetTransform();
   const gfx3DMatrix& currentTransform = layer->GetTransform();
 
   float rootScaleX = rootTransform.GetXScale();
   float rootScaleY = rootTransform.GetYScale();
 
-  if (mIsFirstPaint && metrics) {
+  if (mIsFirstPaint) {
-    mContentRect = metrics->mContentRect;
+    mContentRect = metrics.mContentRect;
-    SetFirstPaintViewport(metrics->mViewportScrollOffset,
+    SetFirstPaintViewport(metrics.mViewportScrollOffset,
                           1/rootScaleX,
                           mContentRect,
-                          metrics->mCSSContentRect);
+                          metrics.mCSSContentRect);
     mIsFirstPaint = false;
-  } else if (metrics && !metrics->mContentRect.IsEqualEdges(mContentRect)) {
+  } else if (!metrics.mContentRect.IsEqualEdges(mContentRect)) {
-    mContentRect = metrics->mContentRect;
+    mContentRect = metrics.mContentRect;
-    SetPageRect(1/rootScaleX, mContentRect, metrics->mCSSContentRect);
+    SetPageRect(1/rootScaleX, mContentRect, metrics.mCSSContentRect);
   }
 
   // We synchronise the viewport information with Java after sending the above
   // notifications, so that Java can take these into account in its response.
-  if (metrics) {
   // Calculate the absolute display port to send to Java
-    nsIntRect displayPort = metrics->mDisplayPort;
+  nsIntRect displayPort = metrics.mDisplayPort;
-    nsIntPoint scrollOffset = metrics->mViewportScrollOffset;
+  nsIntPoint scrollOffset = metrics.mViewportScrollOffset;
   displayPort.x += scrollOffset.x;
   displayPort.y += scrollOffset.y;
 
   SyncViewportInfo(displayPort, 1/rootScaleX, mLayersUpdated,
                    mScrollOffset, mXScale, mYScale);
   mLayersUpdated = false;
-  }
 
   // Handle transformations for asynchronous panning and zooming. We determine the
   // zoom used by Gecko from the transformation set on the root layer, and we
@@ -386,32 +384,18 @@ CompositorParent::TransformShadowTree()
   // primary scrollable layer. We compare this to the desired zoom and scroll
   // offset in the view transform we obtained from Java in order to compute the
   // transformation we need to apply.
-  if (metrics) {
   float tempScaleDiffX = rootScaleX * mXScale;
   float tempScaleDiffY = rootScaleY * mYScale;
 
   nsIntPoint metricsScrollOffset(0, 0);
-    if (metrics->IsScrollable())
+  if (metrics.IsScrollable())
-      metricsScrollOffset = metrics->mViewportScrollOffset;
+    metricsScrollOffset = metrics.mViewportScrollOffset;
 
   nsIntPoint scrollCompensation(
     (mScrollOffset.x / tempScaleDiffX - metricsScrollOffset.x) * mXScale,
     (mScrollOffset.y / tempScaleDiffY - metricsScrollOffset.y) * mYScale);
   ViewTransform treeTransform(-scrollCompensation, mXScale, mYScale);
   shadow->SetShadowTransform(gfx3DMatrix(treeTransform) * currentTransform);
-
-    // Alter the scroll offset so that fixed position layers remain within
-    // the page area.
-    int offsetX = NS_MAX(0, NS_MIN(mScrollOffset.x, mContentRect.width - mWidgetSize.width));
-    int offsetY = NS_MAX(0, NS_MIN(mScrollOffset.y, mContentRect.height - mWidgetSize.height));
-    gfxPoint reverseViewTranslation(offsetX / tempScaleDiffX - metricsScrollOffset.x,
-                                    offsetY / tempScaleDiffY - metricsScrollOffset.y);
-
-    TranslateFixedLayers(layer, reverseViewTranslation);
-  } else {
-    ViewTransform treeTransform(nsIntPoint(0,0), mXScale, mYScale);
-    shadow->SetShadowTransform(gfx3DMatrix(treeTransform) * currentTransform);
-  }
 }
 
 void