Index: compositing_iosurface_layer_mac.mm
===================================================================
--- compositing_iosurface_layer_mac.mm	(revision 280796)
+++ compositing_iosurface_layer_mac.mm	(working copy)
@@ -191,7 +191,7 @@
   TRACE_EVENT0("browser", "CompositingIOSurfaceLayer::drawInCGLContext");
 
   if (!iosurface_->HasIOSurface() || context_->cgl_context() != glContext) {
-    glClearColor(1, 1, 1, 1);
+    glClearColor(0, 0, 0, 0);
     glClear(GL_COLOR_BUFFER_BIT);
     return;
   }
Index: compositing_iosurface_mac.mm
===================================================================
--- compositing_iosurface_mac.mm	(revision 280796)
+++ compositing_iosurface_mac.mm	(working copy)
@@ -350,7 +350,7 @@
     glUseProgram(0); CHECK_AND_SAVE_GL_ERROR();
   } else {
     // Should match the clear color of RenderWidgetHostViewMac.
-    glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
+    glClearColor(0, 0, 0, 0);
     glClear(GL_COLOR_BUFFER_BIT);
   }
 
Index: compositing_iosurface_shader_programs_mac.cc
===================================================================
--- compositing_iosurface_shader_programs_mac.cc	(revision 280796)
+++ compositing_iosurface_shader_programs_mac.cc	(working copy)
@@ -11,6 +11,8 @@
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/strings/stringprintf.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/values.h"
 #include "content/browser/gpu/gpu_data_manager_impl.h"
 #include "gpu/config/gpu_driver_bug_workaround_type.h"
@@ -51,6 +53,7 @@
     }
 );
 
+float bgcolor[] = {1.0f, 1.0f, 1.0f};
 
 // Only calculates position.
 const char kvsSolidWhite[] = GLSL_PROGRAM_AS_STRING(
@@ -238,6 +241,18 @@
   const GLuint shader = glCreateShader(shader_type);
   DCHECK_NE(shader, 0u);
 
+  // Support customization of the background color.
+  std::string bg_shader;
+  if (shader_program == SHADER_PROGRAM_SOLID_WHITE &&
+      shader_type == GL_FRAGMENT_SHADER) {
+    bg_shader = base::StringPrintf(
+        "void main() { gl_FragColor = vec4(%s, %s, %s, 1.0); }",
+        base::DoubleToString(bgcolor[0]).c_str(),
+        base::DoubleToString(bgcolor[1]).c_str(),
+        base::DoubleToString(bgcolor[2]).c_str());
+    kFragmentShaderSourceCodeMap[shader_program] = bg_shader.c_str();
+  }
+
   // Select and compile the shader program source code.
   if (shader_type == GL_VERTEX_SHADER) {
     const GLchar* source_snippets[] = {
@@ -412,6 +427,14 @@
   Reset();
 }
 
+// static
+void CompositingIOSurfaceShaderPrograms::SetBackgroundColor(
+    float r, float g, float b) {
+  bgcolor[0] = r;
+  bgcolor[1] = g;
+  bgcolor[2] = b;
+}
+
 GLuint CompositingIOSurfaceShaderPrograms::GetShaderProgram(int which) {
   if (shader_programs_[which] == 0u) {
     shader_programs_[which] =
Index: compositing_iosurface_shader_programs_mac.h
===================================================================
--- compositing_iosurface_shader_programs_mac.h	(revision 280796)
+++ compositing_iosurface_shader_programs_mac.h	(working copy)
@@ -48,6 +48,8 @@
     return rgb_to_yv12_output_format_;
   }
 
+  static void SetBackgroundColor(float r, float g, float b);
+
  protected:
   FRIEND_TEST_ALL_PREFIXES(CompositingIOSurfaceTransformerTest,
                            TransformsRGBToYV12);
Index: render_widget_host_view_aura.cc
===================================================================
--- render_widget_host_view_aura.cc	(revision 280796)
+++ render_widget_host_view_aura.cc	(working copy)
@@ -1672,8 +1672,14 @@
   // For non-opaque windows, we don't draw anything, since we depend on the
   // canvas coming from the compositor to already be initialized as
   // transparent.
-  if (window_->layer()->fills_bounds_opaquely())
-    canvas->DrawColor(SK_ColorWHITE);
+  if (window_->layer()->fills_bounds_opaquely()) {
+    if (host_->IsRenderView()) {
+      canvas->DrawColor(GetContentClient()->browser()->GetBaseBackgroundColor(
+          RenderViewHost::From(host_)));
+    } else {
+      canvas->DrawColor(SK_ColorWHITE);
+    }
+  }
 }
 
 void RenderWidgetHostViewAura::OnDeviceScaleFactorChanged(
Index: render_widget_host_view_mac.mm
===================================================================
--- render_widget_host_view_mac.mm	(revision 280796)
+++ render_widget_host_view_mac.mm	(working copy)
@@ -504,7 +504,7 @@
 
   background_layer_.reset([[CALayer alloc] init]);
   [background_layer_
-      setBackgroundColor:CGColorGetConstantColor(kCGColorWhite)];
+      setBackgroundColor:CGColorGetConstantColor(kCGColorClear)];
   [background_layer_ setGeometryFlipped:YES];
   [background_layer_ setContentsGravity:kCAGravityTopLeft];
   [cocoa_view_ setLayer:background_layer_];