move colorshader into its own .cpp, add color4f variant

samplecode/GMSampleView.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GMSampleView.h"
 
 GMSampleView::GMSampleView(GM* gm) : fShowSize(false), fGM(gm) {}
@@ skipping 19 matching lines @@
 }
 
 bool GMSampleView::onEvent(const SkEvent& evt) {
     if (evt.isType("GMSampleView::showSize")) {
         fShowSize = SkToBool(evt.getFast32());
         return true;
     }
     return this->INHERITED::onEvent(evt);
 }
 
+#include "SkPicture.h"
+#include "SkStream.h"
+static sk_sp<SkPicture> round_trip_serialize(SkPicture* src) {
+    SkDynamicMemoryWStream stream;
+    src->serialize(&stream);
+    SkAutoTDelete<SkStream> reader(stream.detachAsStream());
+    return SkPicture::MakeFromStream(reader);
+}
+
+#include "SkPictureRecorder.h"
 void GMSampleView::onDrawContent(SkCanvas* canvas) {
+    SkPictureRecorder recorder;
+    SkCanvas* origCanvas = canvas;
+
+    if (false) {
+        SkISize size = fGM->getISize();
+        canvas = recorder.beginRecording(SkRect::MakeIWH(size.width(), size.height()));
+    }
+
     {
         SkAutoCanvasRestore acr(canvas, fShowSize);
         fGM->drawContent(canvas);
     }
+
+    if (origCanvas != canvas) {
+        sk_sp<SkPicture> pic = recorder.finishRecordingAsPicture();
+        if (false) {
+            pic = round_trip_serialize(pic.get());
+        }
+        origCanvas->drawPicture(pic);
+        canvas = origCanvas;
+    }
+
     if (fShowSize) {
         SkISize size = fGM->getISize();
         SkRect r = SkRect::MakeWH(SkIntToScalar(size.width()),
                                   SkIntToScalar(size.height()));
         SkPaint paint;
         paint.setColor(0x40FF8833);
         canvas->drawRect(r, paint);
     }
 }
 
 void GMSampleView::onDrawBackground(SkCanvas* canvas) {
     fGM->drawBackground(canvas);
 }
 
 bool GMSampleView::onAnimate(const SkAnimTimer& timer) {
     return fGM->animate(timer);
 }