#24428 attempted to make surface resizing less expensive by using ANGLE's automatic resizing instead of manually destroying and then re-creating the surface. This caused 
some issues:

1. Flutter's surface size synchronization logic broke: #24682
2. Resizing frameless windows caused the content to wiggle: flutter/flutter#76465

The second issue caused the automatic resizing change to be reverted. However, the first fix was not reverted resulting in an incorrect comment.

Relanding this resizing performance improvement is tracked by flutter/flutter#79427

The original fix had a bad return value that caused the rendering to abort rather than proceed normally without the blurring.

I also changed the color being used so that the contents would show up in golden diffs which use a white background for unrendered pixels.

This change removes the last usages of the Rect internal fields from outside the class, allowing the removal of a `friend` declaration and paving the way to reimplement the Rect methods with ltrb fields.

I tried to do this for Vulkan too but hit the limit of my patience for today on debugging why the Vulkan backend was segfaulting on shutdown.

Half of flutter/flutter#140419