use simpler gradient factories (in prep for removing SkUnitMapper param)

ash/touch/touch_hud_projection.cc

 // Copyright 2013 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 "ash/touch/touch_hud_projection.h"
 
 #include "ash/root_window_controller.h"
 #include "ash/shell.h"
 #include "third_party/skia/include/effects/SkGradientShader.h"
 #include "ui/events/event.h"
@@ skipping 72 matching lines @@
     if (fadeout_)
       alpha = static_cast<int>(fadeout_->CurrentValueBetween(alpha, 0));
     fill_paint_.setAlpha(alpha);
     stroke_paint_.setAlpha(alpha);
     SkShader* shader = SkGradientShader::CreateRadial(
         gradient_center_,
         SkIntToScalar(kPointRadius),
         gradient_colors_,
         gradient_pos_,
         arraysize(gradient_colors_),
-        SkShader::kMirror_TileMode,
-        NULL);
+        SkShader::kMirror_TileMode);
     fill_paint_.setShader(shader);
     shader->unref();
     canvas->DrawCircle(circle_center_, SkIntToScalar(kPointRadius),
                        fill_paint_);
     canvas->DrawCircle(circle_center_, SkIntToScalar(kPointRadius),
                        stroke_paint_);
   }
 
   // Overridden from gfx::AnimationDelegate.
   virtual void AnimationEnded(const gfx::Animation* animation) OVERRIDE {
@@ skipping 73 matching lines @@
     RootWindowController* controller) {
   controller->set_touch_hud_projection(this);
 }
 
 void TouchHudProjection::UnsetHudForRootWindowController(
     RootWindowController* controller) {
   controller->set_touch_hud_projection(NULL);
 }
 
 }  // namespace ash