Adding a didDraw if imageRendering changed in the Style

When changing ImageRendering, there are some cases where it is needed to
check if there is something changing in the canvas.
Adding a DidDraw as a change of imageRendering can produce a redraw of
the canvas.


Bug: 1106978
Change-Id: Icdc6b57eaa94e33279f9eb08c2b3cd807d4a1665
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2391727Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Commit-Queue: Juanmi Huertas <juanmihd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804255}

third_party/blink/renderer/core/html/canvas/html_canvas_element.cc

@@ -1270,11 +1270,25 @@ void HTMLCanvasElement::ContextDestroyed() {
     context_->Stop();
 }
 
+bool HTMLCanvasElement::StyleChangeNeedsDidDraw(
+    const ComputedStyle* old_style,
+    const ComputedStyle& new_style) {
+  // It will only need to redraw for a style change, if the new imageRendering
+  // is different than the previous one, and only if one of the two ir
+  // pixelated.
+  return old_style &&
+         old_style->ImageRendering() != new_style.ImageRendering() &&
+         (old_style->ImageRendering() == EImageRendering::kPixelated ||
+          new_style.ImageRendering() == EImageRendering::kPixelated);
+}
+
 void HTMLCanvasElement::StyleDidChange(const ComputedStyle* old_style,
                                        const ComputedStyle& new_style) {
   UpdateFilterQuality(FilterQualityFromStyle(&new_style));
   if (context_)
     context_->StyleDidChange(old_style, new_style);
+  if (StyleChangeNeedsDidDraw(old_style, new_style))
+    DidDraw();
 }
 
 void HTMLCanvasElement::LayoutObjectDestroyed() {

third_party/blink/renderer/core/html/canvas/html_canvas_element.h

@@ -248,6 +248,8 @@ class CORE_EXPORT HTMLCanvasElement final
   static void RegisterRenderingContextFactory(
       std::unique_ptr<CanvasRenderingContextFactory>);
 
+  bool StyleChangeNeedsDidDraw(const ComputedStyle* old_style,
+                               const ComputedStyle& new_style);
   void StyleDidChange(const ComputedStyle* old_style,
                       const ComputedStyle& new_style);
   void LayoutObjectDestroyed();