Add `SkIRect bounds()` convenience method to SkImageInfo and SkBitmap.

tests/WritePixelsTest.cpp

Index: tests/WritePixelsTest.cpp
diff --git a/tests/WritePixelsTest.cpp b/tests/WritePixelsTest.cpp
index 567d99412ed62eabf4b5b8ea581de3d9985d04f8..eca5adec82639083f3c69d85c97ae9ee60b68d67 100644
--- a/tests/WritePixelsTest.cpp
+++ b/tests/WritePixelsTest.cpp
@@ -195,7 +195,7 @@ static bool check_write(skiatest::Reporter* reporter, SkCanvas* canvas, const Sk
     // At some point this will be unsupported, as we won't allow accessBitmap() to magically call
     // readPixels for the client.
     SkBitmap secretDevBitmap;
-    canvas->readPixels(SkIRect::MakeWH(canvasInfo.width(), canvasInfo.height()), &secretDevBitmap);
+    canvas->readPixels(canvasInfo.bounds(), &secretDevBitmap);
 
     SkAutoLockPixels alp(secretDevBitmap);
     canvasRowBytes = secretDevBitmap.rowBytes();