Always apply UniformMatrix4fvStreamTextureMatrixCHROMIUM matrix argument.

gpu/command_buffer/service/gl_stream_texture_image.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef GPU_COMMAND_BUFFER_SERVICE_GL_STREAM_TEXTURE_IMAGE_H_
 #define GPU_COMMAND_BUFFER_SERVICE_GL_STREAM_TEXTURE_IMAGE_H_
 
 #include "gpu/gpu_export.h"
 #include "ui/gl/gl_image.h"
 
 namespace gpu {
 namespace gles2 {
 
 // Specialization of GLImage that allows us to support (stream) textures
 // that supply a texture matrix.
 class GPU_EXPORT GLStreamTextureImage : public gl::GLImage {
  public:
   GLStreamTextureImage() {}
 
   // Get the matrix.
   // Copy the texture matrix for this image into |matrix|.
   // Subclasses must return a matrix appropriate for a coordinate system where
-  // UV=(0,0) corresponds to the bottom left corner of the image.
+  // UV=(0,0) corresponds to the top left corner of the image.
   virtual void GetTextureMatrix(float matrix[16]) = 0;
 
-  // Copy the texture matrix for this image into |matrix|, returning a matrix
-  // for which UV=(0,0) corresponds to the top left of corner of the image,
-  // which is what Chromium generally expects.
-  void GetFlippedTextureMatrix(float matrix[16]) {
-    GetTextureMatrix(matrix);
-    matrix[13] += matrix[5];
-    matrix[5] = -matrix[5];
-  }
-
   void Flush() override {}
 
  protected:
   ~GLStreamTextureImage() override {}
 
+  // Convenience function for subclasses that deal with SurfaceTextures, whose
+  // coordinate system has (0,0) at the bottom left of the image.
+  // [ a e i m ] [ 1  0 0 0 ]   [ a -e i m+e ]
+  // [ b f j n ] [ 0 -1 0 1 ] = [ b -f j n+f ]
+  // [ c g k o ] [ 0  0 1 0 ]   [ c -g k o+g ]
+  // [ d h l p ] [ 0  0 0 1 ]   [ d -h l p+h ]
+  static void YInvertMatrix(float matrix[16]) {
+    for (int i = 0; i < 4; ++i) {
+      matrix[i + 12] += matrix[i + 4];
+      matrix[i + 4] = -matrix[i + 4];
+    }
+  }
+
  private:
   DISALLOW_COPY_AND_ASSIGN(GLStreamTextureImage);
 };
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_GL_STREAM_TEXTURE_IMAGE_H_