Bug 753058. Add SAMPLE_LABELS for shadows. r=ehsan

This will make this things more obvious on the profile.

layout/base/nsDisplayList.cpp

@@ -1632,6 +1632,7 @@ nsDisplayBoxShadowOuter::Paint(nsDisplayListBuilder* aBuilder,
   nsAutoTArray<nsRect,10> rects;
   ComputeDisjointRectangles(mVisibleRegion, &rects);
 
+  SAMPLE_LABEL("nsDisplayBoxShadowOuter", "Paint");
   for (PRUint32 i = 0; i < rects.Length(); ++i) {
     aCtx->PushState();
     aCtx->IntersectClip(rects[i]);
@@ -1684,6 +1685,7 @@ nsDisplayBoxShadowInner::Paint(nsDisplayListBuilder* aBuilder,
   nsAutoTArray<nsRect,10> rects;
   ComputeDisjointRectangles(mVisibleRegion, &rects);
 
+  SAMPLE_LABEL("nsDisplayBoxShadowInner", "Paint");
   for (PRUint32 i = 0; i < rects.Length(); ++i) {
     aCtx->PushState();
     aCtx->IntersectClip(rects[i]);

layout/generic/nsTextFrameThebes.cpp

@@ -5089,6 +5089,7 @@ nsTextFrame::PaintOneShadow(PRUint32 aOffset, PRUint32 aLength,
                             const nsCharClipDisplayItem::ClipEdges& aClipEdges,
                             nscoord aLeftSideOffset)
 {
+  SAMPLE_LABEL("nsTextFrame", "PaintOneShadow");
   gfxPoint shadowOffset(aShadowDetails->mXOffset, aShadowDetails->mYOffset);
   nscoord blurRadius = NS_MAX(aShadowDetails->mRadius, 0);