rewrite SkMasks::CreateMasks to work in bytesPerPixel

This ought to make it a bit more clear that undefined
shifts (like 1<<31, 1<<32, 1<<33) are not possible,
only 1<<8, 1<<16, 1<<24.

Change-Id: Ia358f9204e5956ba6c23603c5961af86a991b659
Reviewed-on: https://skia-review.googlesource.com/c/192030
Reviewed-by: Leon Scroggins <scroggo@google.com>
Reviewed-by: Greg Kaiser <gkaiser@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
diff --git a/src/gpu/text/GrStrikeCache.cpp b/src/gpu/text/GrStrikeCache.cpp
index 8edc977..293ba29 100644
--- a/src/gpu/text/GrStrikeCache.cpp
+++ b/src/gpu/text/GrStrikeCache.cpp
@@ -17,7 +17,7 @@
 GrStrikeCache::GrStrikeCache(const GrCaps* caps, size_t maxTextureBytes)
         : fPreserveStrike(nullptr)
         , f565Masks(SkMasks::CreateMasks({0xF800, 0x07E0, 0x001F, 0},
-                    GrMaskFormatBytesPerPixel(kA565_GrMaskFormat) * 8)) { }
+                    GrMaskFormatBytesPerPixel(kA565_GrMaskFormat))) { }
 
 GrStrikeCache::~GrStrikeCache() {
     StrikeHash::Iter iter(&fCache);