Implement HiDPI support in Pepper dev interface

ppapi/cpp/dev/view_dev.cc

+// Copyright (c) 2012 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 "ppapi/cpp/dev/view_dev.h"
+
+#include "ppapi/c/dev/ppb_view_dev.h"
+#include "ppapi/cpp/module_impl.h"
+
+namespace pp {
+
+namespace {
+
+template <> const char* interface_name<PPB_View_Dev>() {
+  return PPB_VIEW_DEV_INTERFACE;
+}
+
+}  // namespace
+
+float ViewDev::GetDeviceScale() const {
+  if (has_interface<PPB_View_Dev>()) {

[brettw, 2012/06/19 18:28:21]

It's not clear to me why this remaps error values. I think this should just
return the result of the C interface in all cases except when the interface
doesn't exist (when it should return 1.0 for backward-compat).

In this case, I liked the way you did it for the Graphics2D one better where you
early return if the interface doesn't exist. Same for the function below.

[Josh Horwich, 2012/06/19 23:56:15]

Done.

+    float out = get_interface<PPB_View_Dev>()->GetDeviceScale(pp_resource());
+    if (out > 0.0f)
+      return out;
+  }
+  return 1.0f;
+}
+
+float ViewDev::GetCSSScale() const {
+  if (has_interface<PPB_View_Dev>()) {
+    float out = get_interface<PPB_View_Dev>()->GetCSSScale(pp_resource());
+    if (out > 0.0f)
+      return out;
+  }
+  return 1.0f;
+}
+
+}  // namespace pp