cc: Add pixel tests for transfer function shaders

cc/output/color_lut_cache.cc

Index: cc/output/color_lut_cache.cc
diff --git a/cc/output/color_lut_cache.cc b/cc/output/color_lut_cache.cc
index 1a796dbcf2f23602d6a7d642af80a7968e7ba4cc..f54c1934adfa4b2f7ecc249701e89f0aada1f2d6 100644
--- a/cc/output/color_lut_cache.cc
+++ b/cc/output/color_lut_cache.cc
@@ -81,7 +81,10 @@ unsigned int ColorLUTCache::MakeLUT(const gfx::ColorTransform* transform,
     }
   }
 

[ccameron, 2017/03/23 06:41:40]

This was causing a single-frame flash of strange data (the LUT, interpreted as a
quad texture).

[hubbe, 2017/03/23 18:09:33]

Is this GetInteger slow?
(IE, does it have to fetch data from the GPU process?)
Or does it fetch data from locally cached state?

[ccameron, 2017/03/23 19:21:51]

I'm not 100% sure what the internal implementation is, but I suspect that we
shadow the data on the client side.

[hubbe, 2017/03/23 19:30:40]

If we do not, we should probably investigate if we can just move the GetLUT call
to somewhere where texture binding doesn't mess up the state...

-  unsigned int lut_texture;
+  GLuint previously_bound_texture = 0;
+  GLuint lut_texture = 0;
+  gl_->GetIntegerv(GL_TEXTURE_BINDING_2D,
+                   reinterpret_cast<GLint*>(&previously_bound_texture));
   gl_->GenTextures(1, &lut_texture);
   gl_->BindTexture(GL_TEXTURE_2D, lut_texture);
   gl_->TexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
@@ -92,6 +95,7 @@ unsigned int ColorLUTCache::MakeLUT(const gfx::ColorTransform* transform,
                   lut_samples * lut_samples, 0, GL_RGBA,
                   sizeof(T) == 1 ? GL_UNSIGNED_BYTE : GL_HALF_FLOAT_OES,
                   lut.data());
+  gl_->BindTexture(GL_TEXTURE_2D, previously_bound_texture);
   return lut_texture;
 }