[sensors] Add a browser test to sanity check ambient light sensor.

content/browser/generic_sensor_browsertest.cc

+// Copyright 2016 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 "base/command_line.h"
+#include "base/macros.h"
+#include "base/synchronization/waitable_event.h"
+#include "base/threading/platform_thread.h"
+#include "build/build_config.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/web_contents.h"
+#include "content/public/common/content_switches.h"
+#include "content/public/test/content_browser_test.h"
+#include "content/public/test/content_browser_test_utils.h"
+#include "content/public/test/test_navigation_observer.h"
+#include "content/public/test/test_utils.h"
+#include "content/shell/browser/shell.h"
+#include "content/shell/browser/shell_javascript_dialog_manager.h"
+#include "device/generic_sensor/platform_sensor.h"
+#include "device/generic_sensor/platform_sensor_provider.h"
+#include "device/generic_sensor/sensor_provider_impl.h"
+
+namespace content {
+
+namespace {
+
+class FakeAmbientLightSensor : public device::PlatformSensor {
+ public:
+  FakeAmbientLightSensor(device::mojom::SensorType type,
+                         mojo::ScopedSharedBufferMapping mapping,
+                         device::PlatformSensorProvider* provider)
+      : PlatformSensor(type, std::move(mapping), provider) {}
+
+  device::mojom::ReportingMode GetReportingMode() override {
+    return device::mojom::ReportingMode::ON_CHANGE;
+  }
+
+  bool StartSensor(
+      const device::PlatformSensorConfiguration& configuration) override {
+    device::SensorReading reading;
+    reading.timestamp =
+        (base::TimeTicks::Now() - base::TimeTicks()).InSecondsF();
+    reading.values[0] = 50;
+    UpdateSensorReading(reading, true);
+    return true;
+  }
+
+  void StopSensor() override{};
+
+ protected:
+  ~FakeAmbientLightSensor() override = default;
+  bool CheckSensorConfiguration(
+      const device::PlatformSensorConfiguration& configuration) override {
+    return true;
+  }
+  device::PlatformSensorConfiguration GetDefaultConfiguration() override {
+    device::PlatformSensorConfiguration default_configuration;
+    default_configuration.set_frequency(60);
+    return default_configuration;
+  }
+};
+
+class FakeSensorProvider : public device::PlatformSensorProvider {
+ public:
+  FakeSensorProvider() = default;
+  ~FakeSensorProvider() override = default;
+
+ protected:
+  void CreateSensorInternal(device::mojom::SensorType type,
+                            mojo::ScopedSharedBufferMapping mapping,
+                            const CreateSensorCallback& callback) override {
+    // Create Sensors here.
+    switch (type) {
+      case device::mojom::SensorType::AMBIENT_LIGHT: {
+        scoped_refptr<device::PlatformSensor> sensor =
+            new FakeAmbientLightSensor(type, std::move(mapping), this);
+        callback.Run(std::move(sensor));
+        break;
+      }
+      default:
+        NOTIMPLEMENTED();
+        callback.Run(nullptr);
+    }
+  }
+};
+
+class GenericSensorBrowserTest : public ContentBrowserTest {
+ public:
+  GenericSensorBrowserTest()
+      : io_loop_finished_event_(
+            base::WaitableEvent::ResetPolicy::AUTOMATIC,
+            base::WaitableEvent::InitialState::NOT_SIGNALED) {
+    // TODO(darktears): remove when the GenericSensor feature goes stable.
+    base::CommandLine* cmd_line = base::CommandLine::ForCurrentProcess();
+    cmd_line->AppendSwitchASCII(switches::kEnableFeatures, "GenericSensor");
+  }
+
+  void SetUpOnMainThread() override {
+    BrowserThread::PostTask(
+        BrowserThread::IO, FROM_HERE,
+        base::Bind(&GenericSensorBrowserTest::SetUpOnIOThread,
+                   base::Unretained(this)));
+    io_loop_finished_event_.Wait();
+  }
+
+  void SetUpOnIOThread() {
+    fake_sensor_provider_ = new FakeSensorProvider();
+    device::PlatformSensorProvider::SetProviderForTesting(
+        fake_sensor_provider_);
+    io_loop_finished_event_.Signal();
+  }
+
+  void TearDown() override {
+    device::PlatformSensorProvider::SetProviderForTesting(nullptr);

[Mikhail, 2016/10/26 17:02:12]

^ this also should be done on IO thread.

Think it's better to have 

TearDownOnIOThread() {
device::PlatformSensorProvider::SetProviderForTesting(nullptr);
delete fake_sensor_provider_;
}

and schedule it from TearDown().

+    BrowserThread::DeleteSoon(BrowserThread::IO, FROM_HERE,
+                              fake_sensor_provider_);
+  }
+
+ public:
+  FakeSensorProvider* fake_sensor_provider_;
+  base::WaitableEvent io_loop_finished_event_;
+};
+
+IN_PROC_BROWSER_TEST_F(GenericSensorBrowserTest, AmbientLightSensorTest) {
+  // The test page will create an AmbientLightSensor object in Javascript,
+  // expects to get events with fake values then navigates to #pass.
+  GURL test_url =
+      GetTestUrl("generic_sensor", "ambient_light_sensor_test.html");
+  NavigateToURLBlockUntilNavigationsComplete(shell(), test_url, 2);
+  EXPECT_EQ("pass", shell()->web_contents()->GetLastCommittedURL().ref());
+}
+
+}  //  namespace
+
+}  //  namespace content