PROTOTYPE (incomplete): Add quad renderer and stub bits to handle security warnings.

chrome/browser/android/vr_shell/vr_shell_renderer.cc

 // 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.
 
 #include "chrome/browser/android/vr_shell/vr_shell_renderer.h"
 
 #include <math.h>
 #include <algorithm>
 #include <string>
 
@@ skipping 57 matching lines @@
 #define SHADER(Src) #Src
 #define OEIE_SHADER(Src) "#extension GL_OES_EGL_image_external : require\n" #Src
 #define VOID_OFFSET(x) reinterpret_cast<void*>(x)
 
 const char* GetShaderSource(vr_shell::ShaderID shader) {
   switch (shader) {
     case vr_shell::ShaderID::TEXTURE_QUAD_VERTEX_SHADER:
     case vr_shell::ShaderID::RETICLE_VERTEX_SHADER:
     case vr_shell::ShaderID::LASER_VERTEX_SHADER:
     case vr_shell::ShaderID::CONTROLLER_VERTEX_SHADER:
+    case vr_shell::ShaderID::SKIA_QUAD_VERTEX_SHADER:
       return SHADER(
           /* clang-format off */
           uniform mat4 u_ModelViewProjMatrix;
           attribute vec4 a_Position;
           attribute vec2 a_TexCoordinate;
           varying vec2 v_TexCoordinate;
 
           void main() {
             v_TexCoordinate = a_TexCoordinate;
             gl_Position = u_ModelViewProjMatrix * a_Position;
@@ skipping 24 matching lines @@
           uniform mediump float opacity;
 
           void main() {
             vec2 scaledTex =
                 vec2(u_CopyRect[0] + v_TexCoordinate.x * u_CopyRect[2],
                      u_CopyRect[1] + v_TexCoordinate.y * u_CopyRect[3]);
             lowp vec4 color = texture2D(u_Texture, scaledTex);
             gl_FragColor = vec4(color.xyz, color.w * opacity);
           }
           /* clang-format on */);
+    case vr_shell::ShaderID::SKIA_QUAD_FRAGMENT_SHADER:
+      return OEIE_SHADER(
+          /* clang-format off */
+          precision highp float;
+          uniform sampler2D u_Texture;
+          uniform vec4 u_CopyRect;  // rectangle
+          varying vec2 v_TexCoordinate;
+          uniform lowp vec4 color;
+          uniform mediump float opacity;
+
+          void main() {
+            vec2 scaledTex =
+                vec2(u_CopyRect[0] + v_TexCoordinate.x * u_CopyRect[2],
+                     u_CopyRect[1] + v_TexCoordinate.y * u_CopyRect[3]);
+            lowp vec4 color = texture2D(u_Texture, scaledTex);
+            gl_FragColor = vec4(color.xyz, color.w * opacity);
+          }
+          /* clang-format on */);
     case vr_shell::ShaderID::WEBVR_VERTEX_SHADER:
       return SHADER(
           /* clang-format off */
           attribute vec3 a_Position;
           attribute vec2 a_TexCoordinate;
           varying vec2 v_TexCoordinate;
 
           void main() {
             v_TexCoordinate = a_TexCoordinate;
             gl_Position = vec4(a_Position * 2.0, 1.0);
@@ skipping 259 matching lines @@
 
     quad_queue_.pop();
   }
 
   glDisableVertexAttribArray(position_handle_);
   glDisableVertexAttribArray(tex_coord_handle_);
 }
 
 TexturedQuadRenderer::~TexturedQuadRenderer() = default;
 
+SkiaQuadRenderer::SkiaQuadRenderer()
+    : BaseQuadRenderer(SKIA_QUAD_VERTEX_SHADER,
+                       SKIA_QUAD_FRAGMENT_SHADER) {
+  model_view_proj_matrix_handle_ =
+      glGetUniformLocation(program_handle_, "u_ModelViewProjMatrix");
+  tex_uniform_handle_ = glGetUniformLocation(program_handle_, "u_Texture");
+  copy_rect_uniform_handle_ =
+      glGetUniformLocation(program_handle_, "u_CopyRect");
+  opacity_handle_ = glGetUniformLocation(program_handle_, "opacity");
+}
+
+void SkiaQuadRenderer::Draw(int texture_data_handle,

[cjgrant, 2017/04/19 16:24:52]

This is Flush(), refactored into a queue-less equivalent.  Not yet tested. 
Maybe we can refactor to reuse more code.

+                            const vr::Mat4f& view_proj_matrix,
+                            const gfx::RectF& copy_rect,
+                            float opacity) {
+  TexturedQuad quad;
+  quad.texture_data_handle = texture_data_handle;
+  quad.view_proj_matrix = view_proj_matrix;
+  quad.copy_rect = {copy_rect.x(), copy_rect.y(), copy_rect.width(),
+                    copy_rect.height()};
+  quad.opacity = opacity;
+
+  // Set up GL state that doesn't change between draw calls.
+  glUseProgram(program_handle_);
+
+  glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer_);
+
+  // Set up position attribute.
+  glVertexAttribPointer(position_handle_, kPositionDataSize, GL_FLOAT, false,
+                        kTextureQuadDataStride,
+                        VOID_OFFSET(kPositionDataOffset));
+  glEnableVertexAttribArray(position_handle_);
+
+  // Set up texture coordinate attribute.
+  glVertexAttribPointer(tex_coord_handle_, kTextureCoordinateDataSize, GL_FLOAT,
+                        false, kTextureQuadDataStride,
+                        VOID_OFFSET(kTextureCoordinateDataOffset));
+  glEnableVertexAttribArray(tex_coord_handle_);
+
+  glEnable(GL_BLEND);
+  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
+  // Link texture data with texture unit.
+  glActiveTexture(GL_TEXTURE0);
+  glUniform1i(tex_uniform_handle_, 0);
+
+  glBindTexture(GL_TEXTURE_EXTERNAL_OES, quad.texture_data_handle);
+  glUniform1f(opacity_handle_, quad.opacity);
+
+    // Pass in model view project matrix.
+  glUniformMatrix4fv(model_view_proj_matrix_handle_, 1, false,
+                     MatrixToGLArray(quad.view_proj_matrix).data());
+
+  // Pass in the copy rect.
+  glUniform4fv(copy_rect_uniform_handle_, 1,
+               reinterpret_cast<const float*>(&quad.copy_rect));
+
+  glDrawArrays(GL_TRIANGLES, 0, kVerticesNumber);
+
+  glDisableVertexAttribArray(position_handle_);
+  glDisableVertexAttribArray(tex_coord_handle_);
+}
+
+SkiaQuadRenderer::~SkiaQuadRenderer() = default;
+
 WebVrRenderer::WebVrRenderer()
     : BaseQuadRenderer(WEBVR_VERTEX_SHADER, WEBVR_FRAGMENT_SHADER) {
   tex_uniform_handle_ = glGetUniformLocation(program_handle_, "u_Texture");
 }
 
 // Draw the stereo WebVR frame
 void WebVrRenderer::Draw(int texture_handle) {
   glUseProgram(program_handle_);
 
   // Bind vertex attributes
@@ skipping 324 matching lines @@
       laser_renderer_(base::MakeUnique<LaserRenderer>()),
       controller_renderer_(base::MakeUnique<ControllerRenderer>()),
       gradient_quad_renderer_(base::MakeUnique<GradientQuadRenderer>()),
       gradient_grid_renderer_(base::MakeUnique<GradientGridRenderer>()) {
   BaseQuadRenderer::SetVertexBuffer();
 }
 
 VrShellRenderer::~VrShellRenderer() = default;
 
 }  // namespace vr_shell