RenderEngine: Limit the size of blur input to the display size

Some layers are extraordinarily large. In the particular case we've
found, the layer does not have any content, but even if it did, content
outside the display would not impact the blur. So limit the size of the
rectangle we use for blurring, which in turn limits the size of the
buffers we allocate to compute the blur.

Use the canvas' existing clip, which has already been adjusted to the
size of the display.

Bug: 283427479
Bug: 292539958
Test: manual (logcat)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:763e450b7c5fa6ad1ed35cabb96fdb87467d00c2)
Merged-In: I17e646cce0dca02f4e6a18032ecd1e9120fcf880
Change-Id: I17e646cce0dca02f4e6a18032ecd1e9120fcf880