Bug 907926 - Try avoid having multiple path objects around since this is slow with DrawTargetCairo. r=Bas

layout/base/FrameLayerBuilder.cpp

@@ -3282,6 +3282,7 @@ FrameLayerBuilder::DrawThebesLayer(ThebesLayer* aLayer,
         NS_ASSERTION(commonClipCount < 100,
           "Maybe you really do have more than a hundred clipping rounded rects, or maybe something has gone wrong.");
         currentClip.ApplyTo(aContext, presContext, commonClipCount);
+        aContext->NewPath();
       }
     }
 

layout/base/nsCSSRenderingBorders.cpp

@@ -1579,6 +1579,8 @@ nsCSSBorderRenderer::DrawNoCompositeColorSolidBorderAzure()
     builder->LineTo(strokeEnd);
     RefPtr<Path> path = builder->Finish();
     dt->Stroke(path, ColorPattern(Color::FromABGR(mBorderColors[i])), StrokeOptions(mBorderWidths[i]));
+    builder = nullptr;
+    path = nullptr;
 
     Pattern *pattern;