Ignore CanvasResourceProvider::Clear in OOPR Mode

In OOPR Canvas2D we no longer have access to Skia in the client process.
We need to update CanvasResourceProvider::Clear to not access SkCanvas
in the case of OOPR. A more ideal fix is tracked in
https://crbug.com/1090081 but simply ignoring it is fine for now as
OOPR automatically handles clearing the canvas during initialization.

Bug: 1090083
Change-Id: I5fb75e4fac312ec00b8e5215d3756219672461ee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2236193
Commit-Queue: Nathan Zabriskie <nazabris@microsoft.com>
Reviewed-by: Khushal <khushalsagar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#776618}

third_party/blink/renderer/platform/graphics/canvas_resource_provider.cc

@@ -1150,6 +1150,20 @@ bool CanvasResourceProvider::WritePixels(const SkImageInfo& orig_info,
 }
 
 void CanvasResourceProvider::Clear() {
+  // We don't have an SkCanvas in OOPR mode so we can't do the clear below, plus
+  // OOPR already clears the canvas in BeginRaster.
+  if (IsAccelerated()) {
+    if (!ContextProviderWrapper())
+      return;
+
+    if (ContextProviderWrapper()
+            ->ContextProvider()
+            ->GetCapabilities()
+            .supports_oop_raster) {
+      return;
+    }
+  }
+
   // Clear the background transparent or opaque, as required. This should only
   // be called when a new resource provider is created to ensure that we're
   // not leaking data or displaying bad pixels (in the case of kOpaque