Optionally clear PlatformCanvas instances.

skia/ext/vector_platform_device_skia.cc

 // Copyright (c) 2011 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 "skia/ext/vector_platform_device_skia.h"
 
 #include "skia/ext/bitmap_platform_device.h"
 #include "third_party/skia/include/core/SkClipStack.h"
 #include "third_party/skia/include/core/SkDraw.h"
 #include "third_party/skia/include/core/SkRect.h"
@@ skipping 35 matching lines @@
                                                  height(),
                                                  false, /* not opaque */
                                                  NULL);
 #elif defined(OS_POSIX) && !defined(OS_MACOSX)
   raster_surface_ = BitmapPlatformDevice::Create(width(),
                                                  height(),
                                                  false /* not opaque */);
 #endif
   raster_surface_->unref();  // SkRefPtr and create both took a reference.
 
+#if defined(OS_WIN) || defined(OS_MACOSX)

[vandebo (ex-Chrome), 2012/03/14 23:38:29]

I comment wouldn't hurt here.

[Jeff Timanus, 2012/03/15 19:01:28]

Done.

   SkCanvas canvas(raster_surface_.get());

[vandebo (ex-Chrome), 2012/03/14 23:38:29]

nit: Why is/was this here?

[Jeff Timanus, 2012/03/15 19:01:28]

I noticed this, and was also confused.  I left it as is, because I wanted to
minimize any impact this change may have had.  

It was introduced when the PDF back-end was brought into chrome.  See
http://src.chromium.org/viewvc/chrome?view=rev&revision=80873

[vandebo (ex-Chrome), 2012/03/15 20:40:57]

Ahh - in that revision, the device is cleared to black using the canvas.  At
some point that was removed.

+  canvas.clear(SkColorSetARGB(0, 0, 0, 0));
+#endif
   return raster_surface_->BeginPlatformPaint();
 }
 
 void VectorPlatformDeviceSkia::EndPlatformPaint() {
   DCHECK(raster_surface_ != NULL);
   SkPaint paint;
   // SkPDFDevice checks the passed SkDraw for an empty clip (only).  Fake
   // it out by setting a non-empty clip.
   SkDraw draw;
   SkRegion clip(SkIRect::MakeWH(width(), height()));
@@ skipping 23 matching lines @@
 }
 #elif defined(OS_LINUX) || defined(OS_ANDROID) || defined(OS_OPENBSD)
 void VectorPlatformDeviceSkia::DrawToNativeContext(
     PlatformSurface surface, int x, int y, const PlatformRect* src_rect) {
   // Should never be called on Linux.
   SkASSERT(false);
 }
 #endif
 
 }  // namespace skia