cc: TextureUploader - Reset GL_UNPACK_ALIGNMENT to 4 before uploading images.

cc/resources/texture_uploader.cc

Index: cc/resources/texture_uploader.cc
diff --git a/cc/resources/texture_uploader.cc b/cc/resources/texture_uploader.cc
index 9526fcb9238bdf5f1d4591aab7184c544d0022f2..cc0ec82a19bbfef49ff13add80d8b595db356ab8 100644
--- a/cc/resources/texture_uploader.cc
+++ b/cc/resources/texture_uploader.cc
@@ -196,7 +196,7 @@ void TextureUploader::UploadWithTexSubImage(const uint8* image,
   const uint8* pixel_source;
   unsigned bytes_per_pixel = BitsPerPixel(format) / 8;
   // Use 4-byte row alignment (OpenGL default) for upload performance.
-  // Assuming that GL_UNPACK_ALIGNMENT has not changed from default.
+  // Assuming that GL_UNPACK_ALIGNMENT = 4 is set in UploadWithMapTexSubImage.
   unsigned upload_image_stride =
       RoundUp(bytes_per_pixel * source_rect.width(), 4u);
 
@@ -251,7 +251,7 @@ void TextureUploader::UploadWithMapTexSubImage(const uint8* image,
 
   unsigned bytes_per_pixel = BitsPerPixel(format) / 8;
   // Use 4-byte row alignment (OpenGL default) for upload performance.
-  // Assuming that GL_UNPACK_ALIGNMENT has not changed from default.
+  gl_->PixelStorei(GL_UNPACK_ALIGNMENT, 4);

[danakj, 2014/12/19 20:00:46]

Should we do this when we take control of the context back from ganesh instead
of doing it on every upload? Like we do in GLRenderer:
https://code.google.com/p/chromium/codesearch#chromium/src/cc/output/gl_rende...

[vmiura, 2014/12/19 21:28:16]

If there's a good spot we could do that.

Discussing a bit with Vangelis, we were thinking that as the PixelStorei() call
is not costly compared to actually transferring a texture, then we could put it
here and not be concerned about other code that may inadvertently modify the
state.

   unsigned upload_image_stride =
       RoundUp(bytes_per_pixel * source_rect.width(), 4u);