Only invalidate child clipping mask layer when needed

This patch only invalidates the child clipping mask layer if the size
actually changes. https://crrev.com/564140 regressed performance by
calling this unconditionally.

Because the same bug was made in https://crrev.com/565415, this patch
also updates the two GraphicsLayer::SetSize callsites from that patch.

Bug: 851105
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I74bcda83054e8e21332e723d0fc816910086e2e4
Reviewed-on: https://chromium-review.googlesource.com/1111208Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Commit-Queue: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569645}

third_party/blink/renderer/core/paint/compositing/composited_layer_mapping.cc

@@ -1513,10 +1513,13 @@ void CompositedLayerMapping::UpdateChildContainmentLayerGeometry() {
 
   if (child_clipping_mask_layer_ && !scrolling_layer_ &&
       !GetLayoutObject().Style()->ClipPath()) {
-    child_clipping_mask_layer_->SetSize(child_containment_layer_->Size());
+    if (child_clipping_mask_layer_->Size() !=
+        child_containment_layer_->Size()) {
+      child_clipping_mask_layer_->SetSize(child_containment_layer_->Size());
+      child_clipping_mask_layer_->SetNeedsDisplay();
+    }
     child_clipping_mask_layer_->SetOffsetFromLayoutObject(
         child_containment_layer_->OffsetFromLayoutObject());
-    child_clipping_mask_layer_->SetNeedsDisplay();
   }
 }
 
@@ -1612,10 +1615,12 @@ void CompositedLayerMapping::UpdateScrollingLayerGeometry(
 
   if (child_clipping_mask_layer_ && !GetLayoutObject().Style()->ClipPath()) {
     child_clipping_mask_layer_->SetPosition(scrolling_layer_->GetPosition());
-    child_clipping_mask_layer_->SetSize(scrolling_layer_->Size());
+    if (child_clipping_mask_layer_->Size() != scrolling_layer_->Size()) {
+      child_clipping_mask_layer_->SetSize(scrolling_layer_->Size());
+      child_clipping_mask_layer_->SetNeedsDisplay();
+    }
     child_clipping_mask_layer_->SetOffsetFromLayoutObject(
         ToIntSize(overflow_clip_rect.Location()));
-    child_clipping_mask_layer_->SetNeedsDisplay();
   }
 
   bool overflow_clip_rect_offset_changed =
@@ -1682,10 +1687,12 @@ void CompositedLayerMapping::UpdateChildClippingMaskLayerGeometry() {
   IntRect padding_box = EnclosingIntRect(layout_box.PaddingBoxRect());
 
   child_clipping_mask_layer_->SetPosition(graphics_layer_->GetPosition());
-  child_clipping_mask_layer_->SetSize(graphics_layer_->Size());
+  if (child_clipping_mask_layer_->Size() != graphics_layer_->Size()) {
+    child_clipping_mask_layer_->SetSize(graphics_layer_->Size());
+    child_clipping_mask_layer_->SetNeedsDisplay();
+  }
   child_clipping_mask_layer_->SetOffsetFromLayoutObject(
       ToIntSize(padding_box.Location()));
-  child_clipping_mask_layer_->SetNeedsDisplay();
 
   // NOTE: also some stuff happening in updateChildContainmentLayerGeometry().
 }