media/gpu/VP9Decoder: Set frame size to visible size if it is larger than frame size

VP9Decoder sets visible rectangle to empty if the visible
rectangle obtained from vp9 stream is larger than the frame size.
This causes a regression since M81 because we begin to set
GLImage's dimension to visible size, crrev.com/c/2011583.

This fixes the regression by setting visible rectangle to frame
size in the case.

Bug: b:149727823
Test: HW decoder is used on atlas for VP9 SVC in Meet
Change-Id: Icb47fc99899be3ebde349d6e6005bc8e5a6328a1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2076224Reviewed-by: Andres Calderon Jaramillo <andrescj@chromium.org>
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#745346}

media/gpu/vp9_decoder.cc

@@ -188,12 +188,12 @@ VP9Decoder::DecodeResult VP9Decoder::Decode() {
     gfx::Size new_pic_size = curr_frame_size_;
     gfx::Rect new_render_rect(curr_frame_hdr_->render_width,
                               curr_frame_hdr_->render_height);
-    // For safety, check the validity of render size or leave it as (0, 0).
+    // For safety, check the validity of render size or leave it as pic size.
     if (!gfx::Rect(new_pic_size).Contains(new_render_rect)) {
       DVLOG(1) << "Render size exceeds picture size. render size: "
                << new_render_rect.ToString()
                << ", picture size: " << new_pic_size.ToString();
-      new_render_rect = gfx::Rect();
+      new_render_rect = gfx::Rect(new_pic_size);
     }
     VideoCodecProfile new_profile =
         VP9ProfileToVideoCodecProfile(curr_frame_hdr_->profile);