Split FakeVideoCaptureDevice into classes with single responsibility

media/capture/video/fake_video_capture_device.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 "media/capture/video/fake_video_capture_device.h"
 
 #include <stddef.h>
 #include <algorithm>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/stringprintf.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "media/audio/fake_audio_input_stream.h"
 #include "media/base/video_frame.h"
 #include "mojo/public/cpp/bindings/string.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkMatrix.h"
 #include "third_party/skia/include/core/SkPaint.h"
 #include "ui/gfx/codec/png_codec.h"
 
 namespace media {
 
+namespace {
 // Sweep at 600 deg/sec.
 static const float kPacmanAngularVelocity = 600;
 // Beep every 500 ms.
 static const int kBeepInterval = 500;
 // Gradient travels from bottom to top in 5 seconds.
 static const float kGradientFrequency = 1.f / 5;
 
 static const double kMinZoom = 100.0;
 static const double kMaxZoom = 400.0;
 static const double kZoomStep = 1.0;
+static const double kInitialZoom = 100.0;
+
+static const gfx::Size kSupportedSizes[] = {
+    gfx::Size(96, 96), gfx::Size(320, 240), gfx::Size(640, 480),
+    gfx::Size(1280, 720), gfx::Size(1920, 1080)};
+static const int kSupportedSizesCount =
+    sizeof(kSupportedSizes) / sizeof(gfx::Size);
+
+static const VideoPixelFormat kSupportedPixelFormats[] = {
+    PIXEL_FORMAT_I420, PIXEL_FORMAT_Y16, PIXEL_FORMAT_ARGB};
+
+}  // anonymous namespace
+
+// static
+std::unique_ptr<VideoCaptureDevice> FakeVideoCaptureDeviceMaker::MakeInstance(
+    VideoPixelFormat pixel_format,
+    DeliveryMode delivery_mode,
+    float frame_rate) {
+  bool pixel_format_supported = false;
+  for (const auto& supported_pixel_format : kSupportedPixelFormats) {
+    if (pixel_format == supported_pixel_format) {
+      pixel_format_supported = true;
+      break;
+    }
+  }
+  if (!pixel_format_supported) {
+    DLOG(ERROR) << "Requested an unsupported pixel format "
+                << VideoPixelFormatToString(pixel_format);
+    return nullptr;
+  }
+
+  auto device_state =
+      base::MakeUnique<FakeDeviceState>(kInitialZoom, frame_rate, pixel_format);
+  auto video_frame_painter =
+      base::MakeUnique<PacmanFramePainter>(pixel_format, device_state.get());
+  std::unique_ptr<FrameDeliveryStrategy> frame_delivery_strategy;
+  switch (delivery_mode) {
+    case DeliveryMode::USE_OWN_BUFFERS:
+      frame_delivery_strategy =
+          base::MakeUnique<OwnBufferFrameDeliveryStrategy>();
+      break;
+    case DeliveryMode::USE_CLIENT_BUFFERS:
+      frame_delivery_strategy =
+          base::MakeUnique<ClientBufferFrameDeliveryStrategy>();
+      break;
+  }
+
+  auto photo_frame_painter = base::MakeUnique<PacmanFramePainter>(
+      PIXEL_FORMAT_ARGB, device_state.get());
+  auto photo_device = base::MakeUnique<FakePhotoDevice>(
+      std::move(photo_frame_painter), device_state.get());
+
+  return base::MakeUnique<FakeVideoCaptureDevice>(
+      std::move(video_frame_painter), std::move(frame_delivery_strategy),
+      std::move(photo_device), std::move(device_state));
+}
+
+PacmanFramePainter::PacmanFramePainter(VideoPixelFormat pixel_format,
+                                       const FakeDeviceState* fake_device_state)
+    : pixel_format_(pixel_format), fake_device_state_(fake_device_state) {}
+
+void PacmanFramePainter::PaintFrame(base::TimeDelta elapsed_time,
+                                    uint8_t* target_buffer) {
+  DrawPacman(elapsed_time, target_buffer);
+  DrawGradientSquares(elapsed_time, target_buffer);
+}
 
 // Starting from top left, -45 deg gradient.  Value at point (row, column) is
 // calculated as (top_left_value + (row + column) * step) % MAX_VALUE, where
 // step is MAX_VALUE / (width + height).  MAX_VALUE is 255 (for 8 bit per
 // component) or 65535 for Y16.
 // This is handy for pixel tests where we use the squares to verify rendering.
-void DrawGradientSquares(VideoPixelFormat frame_format,
-                         uint8_t* const pixels,
-                         base::TimeDelta elapsed_time,
-                         const gfx::Size& frame_size) {
-  const int width = frame_size.width();
-  const int height = frame_size.height();
+void PacmanFramePainter::DrawGradientSquares(base::TimeDelta elapsed_time,
+                                             uint8_t* target_buffer) {
+  const int width = fake_device_state_->format.frame_size.width();
+  const int height = fake_device_state_->format.frame_size.height();
+
   const int side = width / 16;  // square side length.
   DCHECK(side);
   const gfx::Point squares[] = {{0, 0},
                                 {width - side, 0},
                                 {0, height - side},
                                 {width - side, height - side}};
   const float start =
       fmod(65536 * elapsed_time.InSecondsF() * kGradientFrequency, 65536);
   const float color_step = 65535 / static_cast<float>(width + height);
   for (const auto& corner : squares) {
     for (int y = corner.y(); y < corner.y() + side; ++y) {
       for (int x = corner.x(); x < corner.x() + side; ++x) {
         const unsigned int value =
             static_cast<unsigned int>(start + (x + y) * color_step) & 0xFFFF;
         size_t offset = (y * width) + x;
-        switch (frame_format) {
+        switch (pixel_format_) {
           case PIXEL_FORMAT_Y16:
-            pixels[offset * sizeof(uint16_t)] = value & 0xFF;
-            pixels[offset * sizeof(uint16_t) + 1] = value >> 8;
+            target_buffer[offset * sizeof(uint16_t)] = value & 0xFF;
+            target_buffer[offset * sizeof(uint16_t) + 1] = value >> 8;
             break;
           case PIXEL_FORMAT_ARGB:
-            pixels[offset * sizeof(uint32_t) + 1] = value >> 8;
-            pixels[offset * sizeof(uint32_t) + 2] = value >> 8;
-            pixels[offset * sizeof(uint32_t) + 3] = value >> 8;
+            target_buffer[offset * sizeof(uint32_t) + 1] = value >> 8;
+            target_buffer[offset * sizeof(uint32_t) + 2] = value >> 8;
+            target_buffer[offset * sizeof(uint32_t) + 3] = value >> 8;
             break;
           default:
-            pixels[offset] = value >> 8;
+            target_buffer[offset] = value >> 8;
             break;
         }
       }
     }
   }
 }
 
-void DrawPacman(VideoPixelFormat frame_format,
-                uint8_t* const data,
-                base::TimeDelta elapsed_time,
-                float frame_rate,
-                const gfx::Size& frame_size,
-                double zoom) {
+void PacmanFramePainter::DrawPacman(base::TimeDelta elapsed_time,
+                                    uint8_t* target_buffer) {
+  const int width = fake_device_state_->format.frame_size.width();
+  const int height = fake_device_state_->format.frame_size.height();
+
   // |kN32_SkColorType| stands for the appropriate RGBA/BGRA format.
-  const SkColorType colorspace = (frame_format == PIXEL_FORMAT_ARGB)
+  const SkColorType colorspace = (pixel_format_ == PIXEL_FORMAT_ARGB)
                                      ? kN32_SkColorType
                                      : kAlpha_8_SkColorType;
   // Skia doesn't support 16 bit alpha rendering, so we 8 bit alpha and then use
   // this as high byte values in 16 bit pixels.
-  const SkImageInfo info = SkImageInfo::Make(
-      frame_size.width(), frame_size.height(), colorspace, kOpaque_SkAlphaType);
+  const SkImageInfo info =
+      SkImageInfo::Make(width, height, colorspace, kOpaque_SkAlphaType);
   SkBitmap bitmap;
   bitmap.setInfo(info);
-  bitmap.setPixels(data);
+  bitmap.setPixels(target_buffer);
   SkPaint paint;
   paint.setStyle(SkPaint::kFill_Style);
   SkCanvas canvas(bitmap);
 
-  const SkScalar unscaled_zoom = zoom / 100.f;
+  const SkScalar unscaled_zoom = fake_device_state_->zoom / 100.f;
   SkMatrix matrix;
-  matrix.setScale(unscaled_zoom, unscaled_zoom, frame_size.width() / 2,
-                  frame_size.height() / 2);
+  matrix.setScale(unscaled_zoom, unscaled_zoom, width / 2, height / 2);
   canvas.setMatrix(matrix);
 
   // Equalize Alpha_8 that has light green background while RGBA has white.
-  if (frame_format == PIXEL_FORMAT_ARGB) {
-    const SkRect full_frame =
-        SkRect::MakeWH(frame_size.width(), frame_size.height());
+  if (pixel_format_ == PIXEL_FORMAT_ARGB) {
+    const SkRect full_frame = SkRect::MakeWH(width, height);
     paint.setARGB(255, 0, 127, 0);
     canvas.drawRect(full_frame, paint);
   }
   paint.setColor(SK_ColorGREEN);
 
   // Draw a sweeping circle to show an animation.
   const float end_angle =
       fmod(kPacmanAngularVelocity * elapsed_time.InSecondsF(), 361);
-  const int radius = std::min(frame_size.width(), frame_size.height()) / 4;
-  const SkRect rect = SkRect::MakeXYWH(frame_size.width() / 2 - radius,
-                                       frame_size.height() / 2 - radius,
+  const int radius = std::min(width, height) / 4;
+  const SkRect rect = SkRect::MakeXYWH(width / 2 - radius, height / 2 - radius,
                                        2 * radius, 2 * radius);
   canvas.drawArc(rect, 0, end_angle, true, paint);
 
   // Draw current time.
   const int milliseconds = elapsed_time.InMilliseconds() % 1000;
   const int seconds = elapsed_time.InSeconds() % 60;
   const int minutes = elapsed_time.InMinutes() % 60;
   const int hours = elapsed_time.InHours();
-  const int frame_count = elapsed_time.InMilliseconds() * frame_rate / 1000;
+  const int frame_count = elapsed_time.InMilliseconds() *
+                          fake_device_state_->format.frame_rate / 1000;
 
   const std::string time_string =
       base::StringPrintf("%d:%02d:%02d:%03d %d", hours, minutes, seconds,
                          milliseconds, frame_count);
   canvas.scale(3, 3);
   canvas.drawText(time_string.data(), time_string.length(), 30, 20, paint);
 
-  if (frame_format == PIXEL_FORMAT_Y16) {
+  if (pixel_format_ == PIXEL_FORMAT_Y16) {
     // Use 8 bit bitmap rendered to first half of the buffer as high byte values
     // for the whole buffer. Low byte values are not important.
-    for (int i = frame_size.GetArea() - 1; i >= 0; --i)
-      data[i * 2 + 1] = data[i];
+    for (int i = (width * height) - 1; i >= 0; --i)
+      target_buffer[i * 2 + 1] = target_buffer[i];
   }
-  DrawGradientSquares(frame_format, data, elapsed_time, frame_size);
 }
 
-// Creates a PNG-encoded frame and sends it back to |callback|. The other
-// parameters are used to replicate the PacMan rendering.
-void DoTakeFakePhoto(VideoCaptureDevice::TakePhotoCallback callback,
-                     const VideoCaptureFormat& capture_format,
-                     base::TimeDelta elapsed_time,
-                     float fake_capture_rate,
-                     uint32_t zoom) {
+FakePhotoDevice::FakePhotoDevice(std::unique_ptr<FramePainter> argb_painter,
+                                 const FakeDeviceState* fake_device_state)
+    : argb_painter_(std::move(argb_painter)),
+      fake_device_state_(fake_device_state) {}
+
+FakePhotoDevice::~FakePhotoDevice() = default;
+
+void FakePhotoDevice::TakePhoto(VideoCaptureDevice::TakePhotoCallback callback,
+                                base::TimeDelta elapsed_time) {
+  // Create a PNG-encoded frame and send it back to |callback|.
   std::unique_ptr<uint8_t[]> buffer(new uint8_t[VideoFrame::AllocationSize(
-      PIXEL_FORMAT_ARGB, capture_format.frame_size)]);
-
-  DrawPacman(PIXEL_FORMAT_ARGB, buffer.get(), elapsed_time, fake_capture_rate,
-             capture_format.frame_size, zoom);
-
+      PIXEL_FORMAT_ARGB, fake_device_state_->format.frame_size)]);
+  argb_painter_->PaintFrame(elapsed_time, buffer.get());
   mojom::BlobPtr blob = mojom::Blob::New();
-  const bool result = gfx::PNGCodec::Encode(
-      buffer.get(), gfx::PNGCodec::FORMAT_RGBA, capture_format.frame_size,
-      capture_format.frame_size.width() * 4, true /* discard_transparency */,
-      std::vector<gfx::PNGCodec::Comment>(), &blob->data);
+  const bool result =
+      gfx::PNGCodec::Encode(buffer.get(), gfx::PNGCodec::FORMAT_RGBA,
+                            fake_device_state_->format.frame_size,
+                            fake_device_state_->format.frame_size.width() * 4,
+                            true /* discard_transparency */,
+                            std::vector<gfx::PNGCodec::Comment>(), &blob->data);
   DCHECK(result);
 
   blob->mime_type = "image/png";
   callback.Run(std::move(blob));
 }
 
-FakeVideoCaptureDevice::FakeVideoCaptureDevice(BufferOwnership buffer_ownership,
-                                               float fake_capture_rate,
-                                               VideoPixelFormat pixel_format)
-    : buffer_ownership_(buffer_ownership),
-      fake_capture_rate_(fake_capture_rate),
-      pixel_format_(pixel_format),
-      current_zoom_(kMinZoom),
+FakeVideoCaptureDevice::FakeVideoCaptureDevice(
+    std::unique_ptr<FramePainter> frame_painter,
+    std::unique_ptr<FrameDeliveryStrategy> frame_delivery_strategy,
+    std::unique_ptr<FakePhotoDevice> photo_device,
+    std::unique_ptr<FakeDeviceState> device_state)
+    : frame_painter_(std::move(frame_painter)),
+      frame_delivery_strategy_(std::move(frame_delivery_strategy)),
+      photo_device_(std::move(photo_device)),
+      device_state_(std::move(device_state)),
       weak_factory_(this) {}
 
 FakeVideoCaptureDevice::~FakeVideoCaptureDevice() {
   DCHECK(thread_checker_.CalledOnValidThread());
 }
 
+// static
+void FakeVideoCaptureDevice::GetSupportedSizes(
+    std::vector<gfx::Size>* supported_sizes) {
+  for (int i = 0; i < kSupportedSizesCount; i++) {
+    supported_sizes->push_back(kSupportedSizes[i]);
+  }
+}
+
+// static
+gfx::Size FakeVideoCaptureDevice::SnapToSupportedSize(
+    const gfx::Size& requested_size) {
+  for (int i = 0; i < kSupportedSizesCount; i++) {
+    const gfx::Size& supported_size = kSupportedSizes[i];
+    if (requested_size.width() <= supported_size.width()) {
+      return supported_size;
+    }
+  }
+  return kSupportedSizes[kSupportedSizesCount - 1];
+}
+
 void FakeVideoCaptureDevice::AllocateAndStart(
     const VideoCaptureParams& params,
     std::unique_ptr<VideoCaptureDevice::Client> client) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
-  client_ = std::move(client);
-
-  // Incoming |params| can be none of the supported formats, so we get the
-  // closest thing rounded up. TODO(mcasas): Use the |params|, if they belong to
-  // the supported ones, when http://crbug.com/309554 is verified.
-  capture_format_.frame_rate = fake_capture_rate_;
-  if (params.requested_format.frame_size.width() > 1280)
-    capture_format_.frame_size.SetSize(1920, 1080);
-  else if (params.requested_format.frame_size.width() > 640)
-    capture_format_.frame_size.SetSize(1280, 720);
-  else if (params.requested_format.frame_size.width() > 320)
-    capture_format_.frame_size.SetSize(640, 480);
-  else if (params.requested_format.frame_size.width() > 96)
-    capture_format_.frame_size.SetSize(320, 240);
-  else
-    capture_format_.frame_size.SetSize(96, 96);
-
-  capture_format_.pixel_format = pixel_format_;
-  if (buffer_ownership_ == BufferOwnership::CLIENT_BUFFERS) {
-    capture_format_.pixel_storage = PIXEL_STORAGE_CPU;
-    capture_format_.pixel_format = PIXEL_FORMAT_ARGB;
-    DVLOG(1) << "starting with client argb buffers";
-  } else if (buffer_ownership_ == BufferOwnership::OWN_BUFFERS) {
-    capture_format_.pixel_storage = PIXEL_STORAGE_CPU;
-    DVLOG(1) << "starting with own " << VideoPixelFormatToString(pixel_format_)
-             << " buffers";
-  }
-
-  if (buffer_ownership_ == BufferOwnership::OWN_BUFFERS) {
-    fake_frame_.reset(new uint8_t[VideoFrame::AllocationSize(
-        pixel_format_, capture_format_.frame_size)]);
-  }
-
   beep_time_ = base::TimeDelta();
   elapsed_time_ = base::TimeDelta();
-
-  if (buffer_ownership_ == BufferOwnership::CLIENT_BUFFERS)
-    BeepAndScheduleNextCapture(
-        base::TimeTicks::Now(),
-        base::Bind(&FakeVideoCaptureDevice::CaptureUsingClientBuffers,
-                   weak_factory_.GetWeakPtr()));
-  else if (buffer_ownership_ == BufferOwnership::OWN_BUFFERS)
-    BeepAndScheduleNextCapture(
-        base::TimeTicks::Now(),
-        base::Bind(&FakeVideoCaptureDevice::CaptureUsingOwnBuffers,
-                   weak_factory_.GetWeakPtr()));
+  device_state_->format.frame_size =
+      SnapToSupportedSize(params.requested_format.frame_size);
+  frame_delivery_strategy_->Initialize(device_state_->format.pixel_format,
+                                       std::move(client), device_state_.get());
+  device_running_ = true;
+  current_session_id_++;
+  BeepAndScheduleNextCapture(base::TimeTicks::Now());
 }
 
 void FakeVideoCaptureDevice::StopAndDeAllocate() {
   DCHECK(thread_checker_.CalledOnValidThread());
-  client_.reset();
+
+  // Update flag to stop the perpetual scheduling of tasks.
+  device_running_ = false;
+  frame_delivery_strategy_->Uninitialize();
 }
 
 void FakeVideoCaptureDevice::GetPhotoCapabilities(
     GetPhotoCapabilitiesCallback callback) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  photo_device_->GetPhotoCapabilities(std::move(callback));
+}
+
+void FakePhotoDevice::GetPhotoCapabilities(
+    VideoCaptureDevice::GetPhotoCapabilitiesCallback callback) {
   mojom::PhotoCapabilitiesPtr photo_capabilities =
       mojom::PhotoCapabilities::New();
   photo_capabilities->iso = mojom::Range::New();
   photo_capabilities->iso->current = 100.0;
   photo_capabilities->iso->max = 100.0;
   photo_capabilities->iso->min = 100.0;
   photo_capabilities->iso->step = 0.0;
   photo_capabilities->height = mojom::Range::New();
-  photo_capabilities->height->current = capture_format_.frame_size.height();
+  photo_capabilities->height->current =
+      fake_device_state_->format.frame_size.height();
   photo_capabilities->height->max = 1080.0;
   photo_capabilities->height->min = 96.0;
   photo_capabilities->height->step = 1.0;
   photo_capabilities->width = mojom::Range::New();
-  photo_capabilities->width->current = capture_format_.frame_size.width();
+  photo_capabilities->width->current =
+      fake_device_state_->format.frame_size.width();
   photo_capabilities->width->max = 1920.0;
   photo_capabilities->width->min = 96.0;
-  photo_capabilities->width->step = 1;
+  photo_capabilities->width->step = 1.0;
   photo_capabilities->zoom = mojom::Range::New();
-  photo_capabilities->zoom->current = current_zoom_;
+  photo_capabilities->zoom->current = fake_device_state_->zoom;
   photo_capabilities->zoom->max = kMaxZoom;
   photo_capabilities->zoom->min = kMinZoom;
   photo_capabilities->zoom->step = kZoomStep;
   photo_capabilities->focus_mode = mojom::MeteringMode::NONE;
   photo_capabilities->exposure_mode = mojom::MeteringMode::NONE;
   photo_capabilities->exposure_compensation = mojom::Range::New();
   photo_capabilities->white_balance_mode = mojom::MeteringMode::NONE;
   photo_capabilities->fill_light_mode = mojom::FillLightMode::NONE;
   photo_capabilities->red_eye_reduction = false;
   photo_capabilities->color_temperature = mojom::Range::New();
   photo_capabilities->brightness = media::mojom::Range::New();
   photo_capabilities->contrast = media::mojom::Range::New();
   photo_capabilities->saturation = media::mojom::Range::New();
   photo_capabilities->sharpness = media::mojom::Range::New();
   callback.Run(std::move(photo_capabilities));
 }
 
 void FakeVideoCaptureDevice::SetPhotoOptions(mojom::PhotoSettingsPtr settings,
                                              SetPhotoOptionsCallback callback) {
-  if (settings->has_zoom)
-    current_zoom_ = std::max(kMinZoom, std::min(settings->zoom, kMaxZoom));
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (settings->has_zoom) {
+    device_state_->zoom =
+        std::max(kMinZoom, std::min(settings->zoom, kMaxZoom));
+  }
+
   callback.Run(true);
 }
 
 void FakeVideoCaptureDevice::TakePhoto(TakePhotoCallback callback) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   base::ThreadTaskRunnerHandle::Get()->PostTask(
-      FROM_HERE,
-      base::Bind(&DoTakeFakePhoto, base::Passed(&callback), capture_format_,
-                 elapsed_time_, fake_capture_rate_, current_zoom_));
+      FROM_HERE, base::Bind(&FakePhotoDevice::TakePhoto,
+                            base::Unretained(photo_device_.get()),
+                            base::Passed(&callback), elapsed_time_));
 }
 
-void FakeVideoCaptureDevice::CaptureUsingOwnBuffers(
-    base::TimeTicks expected_execution_time) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  const size_t frame_size = capture_format_.ImageAllocationSize();
+OwnBufferFrameDeliveryStrategy::OwnBufferFrameDeliveryStrategy() = default;
 
-  memset(fake_frame_.get(), 0, frame_size);
-  DrawPacman(capture_format_.pixel_format, fake_frame_.get(), elapsed_time_,
-             fake_capture_rate_, capture_format_.frame_size, current_zoom_);
-  // Give the captured frame to the client.
+OwnBufferFrameDeliveryStrategy::~OwnBufferFrameDeliveryStrategy() = default;
+
+void OwnBufferFrameDeliveryStrategy::Initialize(
+    VideoPixelFormat pixel_format,
+    std::unique_ptr<VideoCaptureDevice::Client> client,
+    const FakeDeviceState* device_state) {
+  client_ = std::move(client);
+  device_state_ = device_state;
+  buffer_.reset(new uint8_t[VideoFrame::AllocationSize(
+      pixel_format, device_state_->format.frame_size)]);
+}
+
+void OwnBufferFrameDeliveryStrategy::Uninitialize() {
+  client_.reset();
+  device_state_ = nullptr;
+  buffer_.reset();
+}
+
+uint8_t* OwnBufferFrameDeliveryStrategy::PrepareBufferForNextFrame() {
+  if (client_ == nullptr)
+    return nullptr;
+
+  const size_t frame_size = device_state_->format.ImageAllocationSize();
+  memset(buffer_.get(), 0, frame_size);
+  return buffer_.get();
+}
+
+void OwnBufferFrameDeliveryStrategy::DeliverFrame() {
+  if (client_ == nullptr)
+    return;
+  const size_t frame_size = device_state_->format.ImageAllocationSize();
   base::TimeTicks now = base::TimeTicks::Now();
   if (first_ref_time_.is_null())
     first_ref_time_ = now;
-  client_->OnIncomingCapturedData(fake_frame_.get(), frame_size,
-                                  capture_format_, 0 /* rotation */, now,
+  client_->OnIncomingCapturedData(buffer_.get(), frame_size,
+                                  device_state_->format, 0 /* rotation */, now,
                                   now - first_ref_time_);
-  BeepAndScheduleNextCapture(
-      expected_execution_time,
-      base::Bind(&FakeVideoCaptureDevice::CaptureUsingOwnBuffers,
-                 weak_factory_.GetWeakPtr()));
 }
 
-void FakeVideoCaptureDevice::CaptureUsingClientBuffers(
-    base::TimeTicks expected_execution_time) {
-  DCHECK(thread_checker_.CalledOnValidThread());
+ClientBufferFrameDeliveryStrategy::ClientBufferFrameDeliveryStrategy() =
+    default;
+
+ClientBufferFrameDeliveryStrategy::~ClientBufferFrameDeliveryStrategy() =
+    default;
+
+void ClientBufferFrameDeliveryStrategy::Initialize(
+    VideoPixelFormat,
+    std::unique_ptr<VideoCaptureDevice::Client> client,
+    const FakeDeviceState* device_state) {
+  client_ = std::move(client);
+  device_state_ = device_state;
+}
+
+void ClientBufferFrameDeliveryStrategy::Uninitialize() {
+  client_.reset();
+  device_state_ = nullptr;
+}
+
+uint8_t* ClientBufferFrameDeliveryStrategy::PrepareBufferForNextFrame() {
+  if (client_ == nullptr)
+    return nullptr;
 
   const int arbitrary_frame_feedback_id = 0;
-  std::unique_ptr<VideoCaptureDevice::Client::Buffer> capture_buffer(
-      client_->ReserveOutputBuffer(
-          capture_format_.frame_size, capture_format_.pixel_format,
-          capture_format_.pixel_storage, arbitrary_frame_feedback_id));
-  DLOG_IF(ERROR, !capture_buffer) << "Couldn't allocate Capture Buffer";
-  DCHECK(capture_buffer->data()) << "Buffer has NO backing memory";
+  capture_buffer_ = client_->ReserveOutputBuffer(
+      device_state_->format.frame_size, device_state_->format.pixel_format,
+      device_state_->format.pixel_storage, arbitrary_frame_feedback_id);
+  DLOG_IF(ERROR, !capture_buffer_) << "Couldn't allocate Capture Buffer";
+  DCHECK(capture_buffer_->data()) << "Buffer has NO backing memory";
 
-  DCHECK_EQ(PIXEL_STORAGE_CPU, capture_format_.pixel_storage);
-  uint8_t* data_ptr = static_cast<uint8_t*>(capture_buffer->data());
-  memset(data_ptr, 0, capture_buffer->mapped_size());
-  DrawPacman(capture_format_.pixel_format, data_ptr, elapsed_time_,
-             fake_capture_rate_, capture_format_.frame_size, current_zoom_);
+  DCHECK_EQ(device_state_->format.pixel_storage, PIXEL_STORAGE_CPU);
 
-  // Give the captured frame to the client.
+  uint8_t* data_ptr = static_cast<uint8_t*>(capture_buffer_->data());
+  memset(data_ptr, 0, capture_buffer_->mapped_size());
+  return data_ptr;
+}
+
+void ClientBufferFrameDeliveryStrategy::DeliverFrame() {
+  if (client_ == nullptr)
+    return;
+
   base::TimeTicks now = base::TimeTicks::Now();
   if (first_ref_time_.is_null())
     first_ref_time_ = now;
-  client_->OnIncomingCapturedBuffer(std::move(capture_buffer), capture_format_,
-                                    now, now - first_ref_time_);
-
-  BeepAndScheduleNextCapture(
-      expected_execution_time,
-      base::Bind(&FakeVideoCaptureDevice::CaptureUsingClientBuffers,
-                 weak_factory_.GetWeakPtr()));
+  client_->OnIncomingCapturedBuffer(std::move(capture_buffer_),
+                                    device_state_->format, now,
+                                    now - first_ref_time_);
 }
 
 void FakeVideoCaptureDevice::BeepAndScheduleNextCapture(
-    base::TimeTicks expected_execution_time,
-    const base::Callback<void(base::TimeTicks)>& next_capture) {
+    base::TimeTicks expected_execution_time) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   const base::TimeDelta beep_interval =
       base::TimeDelta::FromMilliseconds(kBeepInterval);
   const base::TimeDelta frame_interval =
-      base::TimeDelta::FromMicroseconds(1e6 / fake_capture_rate_);
+      base::TimeDelta::FromMicroseconds(1e6 / device_state_->format.frame_rate);
   beep_time_ += frame_interval;
   elapsed_time_ += frame_interval;
 
   // Generate a synchronized beep twice per second.
   if (beep_time_ >= beep_interval) {
     FakeAudioInputStream::BeepOnce();
     beep_time_ -= beep_interval;
   }
 
   // Reschedule next CaptureTask.
   const base::TimeTicks current_time = base::TimeTicks::Now();
   // Don't accumulate any debt if we are lagging behind - just post the next
   // frame immediately and continue as normal.
   const base::TimeTicks next_execution_time =
       std::max(current_time, expected_execution_time + frame_interval);
   const base::TimeDelta delay = next_execution_time - current_time;
   base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
-      FROM_HERE, base::Bind(next_capture, next_execution_time), delay);
+      FROM_HERE, base::Bind(&FakeVideoCaptureDevice::OnNextFrameDue,
+                            weak_factory_.GetWeakPtr(), next_execution_time,
+                            current_session_id_),
+      delay);
+}
+
+void FakeVideoCaptureDevice::OnNextFrameDue(
+    base::TimeTicks expected_execution_time,
+    int session_id) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (!device_running_)
+    return;
+  if (session_id != current_session_id_)
+    return;
+
+  uint8_t* buffer = frame_delivery_strategy_->PrepareBufferForNextFrame();
+  frame_painter_->PaintFrame(elapsed_time_, buffer);
+  frame_delivery_strategy_->DeliverFrame();
+
+  BeepAndScheduleNextCapture(expected_execution_time);
 }
 
 }  // namespace media