rename FoceCopyMode to SkCopyPixelMode

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2220603002

Review-Url: https://codereview.chromium.org/2220603002
diff --git a/src/image/SkImageShader.cpp b/src/image/SkImageShader.cpp
index a486f71..5fbb0a9 100644
--- a/src/image/SkImageShader.cpp
+++ b/src/image/SkImageShader.cpp
@@ -234,9 +234,14 @@
 
 sk_sp<SkShader> SkMakeBitmapShader(const SkBitmap& src, SkShader::TileMode tmx,
                                    SkShader::TileMode tmy, const SkMatrix* localMatrix,
-                                   SkTBlitterAllocator* allocator) {
-    ForceCopyMode mode = allocator ? kNever_ForceCopyMode : kNo_ForceCopyMode;
-    return SkImageShader::Make(SkMakeImageFromRasterBitmap(src, mode).get(),
+                                   SkCopyPixelsMode cpm, SkTBlitterAllocator* allocator) {
+    // Until we learn otherwise, it seems that any caller that is passing an allocator must be
+    // assuming that the returned shader will have a stack-frame lifetime, so we assert that
+    // they are also asking for kNever_SkCopyPixelsMode. If that proves otherwise, we can remove
+    // or modify this assert.
+    SkASSERT(!allocator || (kNever_SkCopyPixelsMode == cpm));
+
+    return SkImageShader::Make(SkMakeImageFromRasterBitmap(src, cpm).get(),
                                tmx, tmy, localMatrix, allocator);
 }