Fixes use-of-uninitialized-value MSan error in image_skia_unittest

The existing test code returns an empty ImageSkiaRep where
bytes are allocated but nothing is initialized. This was okay
because ImageSkiaTest doesn't touch the contents of the image.

Now ImageSkia can rescale the image data and such cases are
tested. So using a dummy ImageSkiaRep wouldn't be helthy.
Rather some data should be drawn.

BUG=373748
R=oshima@chromium.org
TEST=

Review URL: https://codereview.chromium.org/285393002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270970 0039d316-1c4b-4281-b951-d872f2087c98

ui/gfx/image/image_skia_rep.cc

@@ -19,6 +19,7 @@ ImageSkiaRep::ImageSkiaRep(const gfx::Size& size, float scale) : scale_(scale) {
                     static_cast<int>(size.width() * this->scale()),
                     static_cast<int>(size.height() * this->scale()));
   bitmap_.allocPixels();
+  bitmap_.eraseColor(SK_ColorRED);
 }
 
 ImageSkiaRep::ImageSkiaRep(const SkBitmap& src, float scale)

ui/gfx/image/image_skia_rep.h

@@ -21,9 +21,9 @@ class GFX_EXPORT ImageSkiaRep {
   ~ImageSkiaRep();
 
   // Creates a bitmap with kARGB_8888_Config config with given |size| in DIP.
-  // This allocates pixels in the bitmap. Specifying 0 scale means the image
-  // is for unscaled image. (unscaled() returns truen, and scale() returns
-  // 1.0f;)
+  // This allocates pixels in the bitmap and fill the bitmap with a color.
+  // Specifying 0 scale means the image is for unscaled image. (unscaled()
+  // returns truen, and scale() returns 1.0f;)
   ImageSkiaRep(const gfx::Size& size, float scale);
 
   // Creates a bitmap with given scale.