Fix VideoFrame ctor crash

This CL fixes VideoFrame constructor crash, when it is passed a closed
ImageBitmap. This happens because the passed pointer is valid, but we
use ImageBitmap::ImageBitmap() without checking its returns value.

Change-Id: I04858a194026f3448e40a62d556153c32c8bdde1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2357458
Commit-Queue: Thomas Guilbert <tguilbert@chromium.org>
Auto-Submit: Thomas Guilbert <tguilbert@chromium.org>
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798385}

third_party/blink/renderer/modules/webcodecs/video_frame.cc

@@ -97,17 +97,18 @@ VideoFrame* VideoFrame::Create(ImageBitmap* source,
                                       "No source was provided");
     return nullptr;
   }
-  gfx::Size size(source->width(), source->height());
-  gfx::Rect rect(size);
-  base::TimeDelta timestamp =
-      base::TimeDelta::FromMicroseconds(init->timestamp());
 
-  if (!source) {
+  if (!source->BitmapImage()) {
     exception_state.ThrowDOMException(DOMExceptionCode::kInvalidStateError,
                                       "Invalid source state");
     return nullptr;
   }
 
+  gfx::Size size(source->width(), source->height());
+  gfx::Rect rect(size);
+  base::TimeDelta timestamp =
+      base::TimeDelta::FromMicroseconds(init->timestamp());
+
   auto sk_image =
       source->BitmapImage()->PaintImageForCurrentFrame().GetSkImage();
   auto sk_color_space = sk_image->refColorSpace();