Refactor the Get*Hardware* routines a bit.

content/renderer/media/audio_hardware.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 "content/renderer/media/audio_hardware.h"
+
+#include "base/logging.h"
+#include "content/common/view_messages.h"
+#include "content/renderer/render_thread_impl.h"
+
+static double output_sample_rate = 0.0;
+static double input_sample_rate = 0.0;
+static size_t output_buffer_size = 0;
+
+namespace audio_hardware {
+
+double GetOutputSampleRate() {
+  DCHECK(RenderThreadImpl::current() != NULL);
+
+  if (!output_sample_rate) {
+    RenderThreadImpl::current()->Send(
+        new ViewHostMsg_GetHardwareSampleRate(&output_sample_rate));
+  }
+  return output_sample_rate;
+}
+
+double GetInputSampleRate() {
+  DCHECK(RenderThreadImpl::current() != NULL);
+
+  if (!input_sample_rate) {
+    RenderThreadImpl::current()->Send(
+        new ViewHostMsg_GetHardwareInputSampleRate(&input_sample_rate));
+  }
+  return input_sample_rate;
+}
+
+size_t GetOutputBufferSize() {
+  DCHECK(RenderThreadImpl::current() != NULL);
+
+  if (!output_buffer_size) {
+    uint32 buffer_size = 0;
+    RenderThreadImpl::current()->Send(
+        new ViewHostMsg_GetHardwareBufferSize(&buffer_size));
+    output_buffer_size = buffer_size;
+  }
+
+  return output_buffer_size;
+}
+
+void ResetCache() {
+  DCHECK(RenderThreadImpl::current() != NULL);
+
+  output_sample_rate = 0.0;
+  input_sample_rate = 0.0;
+  output_buffer_size = 0;
+}
+
+}  // namespace audio_hardware