Test gpu memory buffers drawing directly to the backbuffer.

To test the lifecycle of a memory buffer we used to use
glCopyTextureCHROMIUM. This has some limitations due to the extension
spec (i.e: limited subset of formats), and doesn't test the general
lifecycle of the memory buffer.

This patch changes GpuMemoryBufferTest.Lifecycle to test the lifecycle
of the GpuMemoryBuffer writing directly to the backbuffer.

BUG=

Review URL: https://codereview.chromium.org/1066073002

Cr-Commit-Position: refs/heads/master@{#324123}

gpu/command_buffer/tests/gl_gpu_memory_buffer_unittest.cc

@@ -38,40 +38,45 @@ class GpuMemoryBufferTest
     : public testing::TestWithParam<gfx::GpuMemoryBuffer::Format> {
  protected:
   void SetUp() override {
-    gl_.Initialize(GLManager::Options());
+    GLManager::Options options;
+    options.size = gfx::Size(kImageWidth, kImageHeight);
+    gl_.Initialize(options);
     gl_.MakeCurrent();
-
-    glGenTextures(2, texture_ids_);
-    glBindTexture(GL_TEXTURE_2D, texture_ids_[1]);
-
-    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
-    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
-    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
-
-    glGenFramebuffers(1, &framebuffer_id_);
-    glBindFramebuffer(GL_FRAMEBUFFER, framebuffer_id_);
-    glFramebufferTexture2D(GL_FRAMEBUFFER,
-                           GL_COLOR_ATTACHMENT0,
-                           GL_TEXTURE_2D,
-                           texture_ids_[1],
-                           0);
   }
 
   void TearDown() override {
-    glDeleteTextures(2, texture_ids_);
-    glDeleteFramebuffers(1, &framebuffer_id_);
-
     gl_.Destroy();
   }
 
   GLManager gl_;
-  GLuint texture_ids_[2];
-  GLuint framebuffer_id_;
 };
 
 namespace {
 
+#define SHADER(Src) #Src
+
+// clang-format off
+const char kVertexShader[] =
+SHADER(
+  attribute vec4 a_position;
+  varying vec2 v_texCoord;
+  void main() {
+    gl_Position = a_position;
+    v_texCoord = vec2((a_position.x + 1.0) * 0.5, (a_position.y + 1.0) * 0.5);
+  }
+);
+
+const char* kFragmentShader =
+SHADER(
+  precision mediump float;
+  uniform sampler2D a_texture;
+  varying vec2 v_texCoord;
+  void main() {
+    gl_FragColor = texture2D(a_texture, v_texCoord);
+  }
+);
+// clang-format on
+
 std::vector<uint8> GetTexturePixel(const gfx::GpuMemoryBuffer::Format format) {
   std::vector<uint8> pixel;
   switch (format) {
@@ -150,6 +155,16 @@ GLenum InternalFormat(gfx::GpuMemoryBuffer::Format format) {
 
 // An end to end test that tests the whole GpuMemoryBuffer lifecycle.
 TEST_P(GpuMemoryBufferTest, Lifecycle) {
+  GLuint texture_id = 0;
+  glGenTextures(1, &texture_id);
+  ASSERT_NE(0u, texture_id);
+  glBindTexture(GL_TEXTURE_2D, texture_id);
+  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+
+  // Create the gpu memory buffer.
   scoped_ptr<gfx::GpuMemoryBuffer> buffer(gl_.CreateGpuMemoryBuffer(
       gfx::Size(kImageWidth, kImageHeight), GetParam()));
 
@@ -180,17 +195,31 @@ TEST_P(GpuMemoryBufferTest, Lifecycle) {
   GLuint image_id =
       glCreateImageCHROMIUM(buffer->AsClientBuffer(), kImageWidth, kImageHeight,
                             InternalFormat(GetParam()));
-  EXPECT_NE(0u, image_id);
-  EXPECT_TRUE(gl_.decoder()->GetImageManager()->LookupImage(image_id) != NULL);
+  ASSERT_NE(0u, image_id);
+  ASSERT_TRUE(gl_.decoder()->GetImageManager()->LookupImage(image_id) != NULL);
 
-  // Bind the texture and the image.
-  glBindTexture(GL_TEXTURE_2D, texture_ids_[0]);
+  // Bind the image.
   glBindTexImage2DCHROMIUM(GL_TEXTURE_2D, image_id);
 
-  // Copy texture so we can verify result using CheckPixels.
-  glCopyTextureCHROMIUM(GL_TEXTURE_2D, texture_ids_[0], texture_ids_[1],
-                        InternalFormat(GetParam()), GL_UNSIGNED_BYTE);
-  EXPECT_TRUE(glGetError() == GL_NO_ERROR);
+  // Build program, buffers and draw the texture.
+  GLuint vertex_shader =
+      GLTestHelper::LoadShader(GL_VERTEX_SHADER, kVertexShader);
+  GLuint fragment_shader =
+      GLTestHelper::LoadShader(GL_FRAGMENT_SHADER, kFragmentShader);
+  GLuint program = GLTestHelper::SetupProgram(vertex_shader, fragment_shader);
+  ASSERT_NE(0u, program);
+  glUseProgram(program);
+
+  GLint sampler_location = glGetUniformLocation(program, "a_texture");
+  ASSERT_NE(-1, sampler_location);
+  glUniform1i(sampler_location, 0);
+
+  GLuint vbo =
+      GLTestHelper::SetupUnitQuad(glGetAttribLocation(program, "a_position"));
+  ASSERT_NE(0u, vbo);
+  glViewport(0, 0, kImageWidth, kImageHeight);
+  glDrawArrays(GL_TRIANGLES, 0, 6);
+  ASSERT_TRUE(glGetError() == GL_NO_ERROR);
 
   // Check if pixels match the values that were assigned to the mapped buffer.
   GLTestHelper::CheckPixels(0, 0, kImageWidth, kImageHeight, 0,
@@ -200,8 +229,13 @@ TEST_P(GpuMemoryBufferTest, Lifecycle) {
   // Release the image.
   glReleaseTexImage2DCHROMIUM(GL_TEXTURE_2D, image_id);
 
-  // Destroy the image.
+  // Clean up.
+  glDeleteProgram(program);
+  glDeleteShader(vertex_shader);
+  glDeleteShader(fragment_shader);
+  glDeleteBuffers(1, &vbo);
   glDestroyImageCHROMIUM(image_id);
+  glDeleteTextures(1, &texture_id);
 }
 
 INSTANTIATE_TEST_CASE_P(GpuMemoryBufferTests,