guard old apis for querying byte-size of a bitmap/imageinfo/pixmap

Previously we had size_t and uint64_t variations.

The new (simpler) API always..
- returns size_t, or 0 if the calculation overflowed
- returns the trimmed size (does not include rowBytes padding for the last row)

Bug: skia:
Change-Id: I05173e877918327c7b207d2f7f1ab0db36892e2e
Reviewed-on: https://skia-review.googlesource.com/50980
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Reviewed-by: Leon Scroggins <scroggo@google.com>
diff --git a/src/core/SkSpecialImage.cpp b/src/core/SkSpecialImage.cpp
index db40329..db4fadc 100644
--- a/src/core/SkSpecialImage.cpp
+++ b/src/core/SkSpecialImage.cpp
@@ -219,7 +219,7 @@
 
     SkAlphaType alphaType() const override { return fBitmap.alphaType(); }
 
-    size_t getSize() const override { return fBitmap.getSize(); }
+    size_t getSize() const override { return fBitmap.computeByteSize(); }
 
     void onDraw(SkCanvas* canvas, SkScalar x, SkScalar y, const SkPaint* paint) const override {
         SkRect dst = SkRect::MakeXYWH(x, y,