gpu: Use a VAO as required by the core profile in ClearFramebuffer

gpu/command_buffer/service/gles2_cmd_clear_framebuffer.cc

Index: gpu/command_buffer/service/gles2_cmd_clear_framebuffer.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_clear_framebuffer.cc b/gpu/command_buffer/service/gles2_cmd_clear_framebuffer.cc
index 6a21c49fd9a05c5f9b8afb82cb66e26a3efa1024..d42dd195820396f04de09b9a9db43d3ef6f87fc0 100644
--- a/gpu/command_buffer/service/gles2_cmd_clear_framebuffer.cc
+++ b/gpu/command_buffer/service/gles2_cmd_clear_framebuffer.cc
@@ -56,9 +56,10 @@ void CompileShader(GLuint shader, const char* shader_source) {
 namespace gpu {
 
 ClearFramebufferResourceManager::ClearFramebufferResourceManager(
-    const gles2::GLES2Decoder* decoder)
-    : initialized_(false), program_(0u), buffer_id_(0u) {
-  Initialize(decoder);
+    const gles2::GLES2Decoder* decoder,
+    const gles2::FeatureInfo::FeatureFlags& feature_flags)
+    : initialized_(false), program_(0u), vao_(0), buffer_id_(0u) {
+  Initialize(decoder, feature_flags);
 }
 
 ClearFramebufferResourceManager::~ClearFramebufferResourceManager() {
@@ -67,12 +68,13 @@ ClearFramebufferResourceManager::~ClearFramebufferResourceManager() {
 }
 
 void ClearFramebufferResourceManager::Initialize(
-    const gles2::GLES2Decoder* decoder) {
+    const gles2::GLES2Decoder* decoder,
+    const gles2::FeatureInfo::FeatureFlags& feature_flags) {
   static_assert(
       kVertexPositionAttrib == 0u,
       "kVertexPositionAttrib must be 0");
-  DCHECK(!buffer_id_);
 
+  DCHECK(!buffer_id_);
   glGenBuffersARB(1, &buffer_id_);
   glBindBuffer(GL_ARRAY_BUFFER, buffer_id_);
   const GLfloat kQuadVertices[] = {-1.0f, -1.0f,
@@ -81,6 +83,19 @@ void ClearFramebufferResourceManager::Initialize(
                                    -1.0f,  1.0f};
   glBufferData(
       GL_ARRAY_BUFFER, sizeof(kQuadVertices), kQuadVertices, GL_STATIC_DRAW);
+
+  DCHECK(!vao_);
+
+  if (feature_flags.native_vertex_array_object) {
+    glGenVertexArraysOES(1, &vao_);
+
+    glBindVertexArrayOES(vao_);
+    glEnableVertexAttribArray(kVertexPositionAttrib);
+    glVertexAttribPointer(kVertexPositionAttrib, 2, GL_FLOAT, GL_FALSE, 0, 0);
+
+    decoder->RestoreAllAttributes();
+  }
+
   decoder->RestoreBufferBindings();
   initialized_ = true;
 }
@@ -90,6 +105,12 @@ void ClearFramebufferResourceManager::Destroy() {
     return;
 
   glDeleteProgram(program_);
+
+  if (vao_ != 0) {
+    glDeleteVertexArraysOES(1, &vao_);
+    vao_ = 0;
+  }
+
   glDeleteBuffersARB(1, &buffer_id_);
   buffer_id_ = 0;
 }
@@ -140,11 +161,14 @@ void ClearFramebufferResourceManager::ClearFramebuffer(
     DLOG(ERROR) << "Invalid shader.";
 #endif
 
-  decoder->ClearAllAttributes();
-  glEnableVertexAttribArray(kVertexPositionAttrib);
-
-  glBindBuffer(GL_ARRAY_BUFFER, buffer_id_);
-  glVertexAttribPointer(kVertexPositionAttrib, 2, GL_FLOAT, GL_FALSE, 0, 0);
+  if (vao_) {
+    glBindVertexArrayOES(vao_);
+  } else {
+    decoder->ClearAllAttributes();
+    glBindBuffer(GL_ARRAY_BUFFER, buffer_id_);
+    glEnableVertexAttribArray(kVertexPositionAttrib);
+    glVertexAttribPointer(kVertexPositionAttrib, 2, GL_FLOAT, GL_FALSE, 0, 0);
+  }
 
   glUniform1f(depth_handle_, clear_depth_value);
   glUniform4f(color_handle_, clear_color_red, clear_color_green,
@@ -179,9 +203,11 @@ void ClearFramebufferResourceManager::ClearFramebuffer(
   glViewport(0, 0, framebuffer_size.width(), framebuffer_size.height());
   glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
 
+  if (vao_ == 0) {
+    decoder->RestoreBufferBindings();
+  }
   decoder->RestoreAllAttributes();
   decoder->RestoreProgramBindings();
-  decoder->RestoreBufferBindings();
   decoder->RestoreGlobalState();
 }