Check that render-frame is valid before returning audio params in Blink.

content/renderer/blink_platform_audio_hardware_browsertest.cc

+// Copyright 2017 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/public/test/render_view_test.h"
+#include "third_party/WebKit/public/platform/Platform.h"
+
+namespace content {
+
+class BlinkPlatformAudioHardwareTest : public RenderViewTest {
+ protected:
+  void SetUp() override { RenderViewTest::SetUp(); }
+};
+
+// Test that calling audioHardware functions from blink::Platform without a v8
+// context returns valid values.
+TEST_F(BlinkPlatformAudioHardwareTest, AudioHardwareFunctionsNoV8) {
+  blink::Platform* blink_platform = blink::Platform::current();
+  size_t buffer_size = blink_platform->audioHardwareBufferSize();
+  EXPECT_GT(buffer_size, 0u);
+  unsigned channels = blink_platform->audioHardwareOutputChannels();
+  EXPECT_GT(channels, 0u);
+  double sample_rate = blink_platform->audioHardwareSampleRate();
+  EXPECT_GT(sample_rate, 0.0);
+}
+
+}  // namespace content