Implement HiDPI support in Pepper dev interface

ppapi/api/dev/ppb_graphics_2d_dev.idl

+/* 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.
+ */
+
+/* This file contains the <code>PPB_Graphics2D_Dev</code> interface. */
+label Chrome {
+  M22 = 0.1
+};
+
+/* PPB_Graphics2D_Dev interface */
+interface PPB_Graphics2D_Dev {
+  /**
+   * SetScale() sets the scale factor that will be applied when painting the
+   * graphics context onto the output device. Typically, if rendering at device
+   * resolution is desired, the context would be created with the width and
+   * height scaled up by the view's GetDeviceScale and SetScale called with a
+   * scale of 1.0 / GetDeviceScale(). For example, if the view resource passed
+   * to DidChangeView has a rectangle of (w=200, h=100) and a device scale of
+   * 2.0, one would call Create with a size of (w=400, h=200) and then call
+   * SetScale with 0.5. One would then treat each pixel in the context as a
+   * single device pixel.
+   *
+   * @param[in] resource A <code>Graphics2D</code> context resource. 
+   * @param[in] scale The scale to apply when painting.
+   *
+   * @return Returns <code>PP_TRUE</code> on success or <code>PP_FALSE</code> if
+   * the resource is invalid or the scale factor is 0 or less.
+   */
+  PP_Bool SetScale(
+      [in] PP_Resource resource,
+      [in] float_t scale);
+
+  /***
+   * GetScale() gets the scale factor that will be applied when painting the
+   * graphics context onto the output device.
+   *
+   * @param[in] resource A <code>Graphics2D</code> context resource.
+   *
+   * @return Returns the scale factor for the graphics context. If the resource
+   * is not a valid <code>Graphics2D</code> context, this will return 0.0.
+   */
+  float_t GetScale(
+      [in] PP_Resource resource);
+}; 
+