Refactor OffscreenCanvas SetSize method

In the past we were calling UpdateMemoryUsage with the old size.
Make it clear that the canvas is being reset if the size is not
changing.

Change-Id: Iea8b9d50ce4b01b82611bc8ff665b5cf673f79db
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1829801
Commit-Queue: Aaron Krajeski <aaronhk@chromium.org>
Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700836}

third_party/blink/renderer/core/offscreencanvas/offscreen_canvas.cc

@@ -120,25 +120,30 @@ void OffscreenCanvas::setHeight(unsigned height) {
 }
 
 void OffscreenCanvas::SetSize(const IntSize& size) {
-  if (context_) {
-    if (context_->Is3d()) {
-      if (size != size_)
-        context_->Reshape(size.Width(), size.Height());
-    } else if (context_->Is2d()) {
+  // Setting size of a canvas also resets it.
+  if (size == size_) {
+    if (context_ && context_->Is2d()) {
       context_->Reset();
       origin_clean_ = true;
     }
+    return;
   }
-  if (size != size_) {
-    UpdateMemoryUsage();
-  }
+
   size_ = size;
+  UpdateMemoryUsage();
+  current_frame_damage_rect_ = SkIRect::MakeWH(size_.Width(), size_.Height());
+
   if (frame_dispatcher_)
     frame_dispatcher_->Reshape(size_);
-
-  current_frame_damage_rect_ = SkIRect::MakeWH(size_.Width(), size_.Height());
-  if (context_)
+  if (context_) {
+    if (context_->Is3d()) {
+      context_->Reshape(size_.Width(), size_.Height());
+    } else if (context_->Is2d()) {
+      context_->Reset();
+      origin_clean_ = true;
+    }
     context_->DidDraw();
+  }
 }
 
 void OffscreenCanvas::RecordTransfer() {