cc: Move image decodes from tile manager to a separate file.

cc/tiles/image_decode_controller.cc

+// Copyright 2015 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 "cc/tiles/image_decode_controller.h"
+
+#include "cc/debug/devtools_instrumentation.h"
+
+namespace cc {
+namespace {
+
+class ImageDecodeTaskImpl : public ImageDecodeTask {
+ public:
+  ImageDecodeTaskImpl(ImageDecodeController* controller,
+                      SkPixelRef* pixel_ref,
+                      int layer_id,
+                      uint64_t source_prepare_tiles_id)
+      : controller_(controller),
+        pixel_ref_(skia::SharePtr(pixel_ref)),
+        layer_id_(layer_id),
+        source_prepare_tiles_id_(source_prepare_tiles_id) {}
+
+  // Overridden from Task:
+  void RunOnWorkerThread() override {
+    TRACE_EVENT1("cc", "ImageDecodeTaskImpl::RunOnWorkerThread",
+                 "source_prepare_tiles_id", source_prepare_tiles_id_);
+    devtools_instrumentation::ScopedImageDecodeTask image_decode_task(
+        pixel_ref_.get());
+    controller_->DecodePixelRef(pixel_ref_.get());
+
+    // Release the reference after decoding image to ensure that it is not kept
+    // alive unless needed.
+    pixel_ref_.clear();
+  }
+
+  // Overridden from TileTask:
+  void ScheduleOnOriginThread(TileTaskClient* client) override {}
+  void CompleteOnOriginThread(TileTaskClient* client) override {}
+  void RunReplyOnOriginThread() override {
+    controller_->OnImageDecodeTaskCompleted(layer_id_, pixel_ref_.get(),
+                                            !HasFinishedRunning());
+  }
+
+ protected:
+  ~ImageDecodeTaskImpl() override {}
+
+ private:
+  ImageDecodeController* controller_;
+  skia::RefPtr<SkPixelRef> pixel_ref_;
+  int layer_id_;
+  uint64_t source_prepare_tiles_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(ImageDecodeTaskImpl);
+};
+
+}  // namespace
+
+ImageDecodeController::ImageDecodeController() {}
+
+ImageDecodeController::~ImageDecodeController() {}
+
+scoped_refptr<ImageDecodeTask> ImageDecodeController::GetTaskForPixelRef(
+    SkPixelRef* pixel_ref,
+    int layer_id,
+    uint64_t prepare_tiles_id) {
+  uint32_t generation_id = pixel_ref->getGenerationID();
+  auto& decode_task = image_decode_tasks_[layer_id][generation_id];
+  // Only decode once per pixel ref.
+  if (decode_task)

[ericrk, 2015/07/30 22:59:30]

super nit: Why not just do "if (!decode_task) decode_task = Create...."

allowing for only one return and simplifying flow a bit?

[vmpstr, 2015/07/30 23:08:34]

Done.

+    return decode_task;
+
+  decode_task = CreateTaskForPixelRef(pixel_ref, layer_id, prepare_tiles_id);
+  return decode_task;
+}
+
+scoped_refptr<ImageDecodeTask> ImageDecodeController::CreateTaskForPixelRef(
+    SkPixelRef* pixel_ref,
+    int layer_id,
+    uint64_t prepare_tiles_id) {
+  return make_scoped_refptr(
+      new ImageDecodeTaskImpl(this, pixel_ref, layer_id, prepare_tiles_id));
+}
+
+void ImageDecodeController::DecodePixelRef(SkPixelRef* pixel_ref) const {
+  // This will cause the image referred to by pixel ref to be decoded.
+  pixel_ref->lockPixels();
+  pixel_ref->unlockPixels();
+}
+
+void ImageDecodeController::AddLayerUsedCount(int layer_id) {
+  ++used_layer_counts_[layer_id];
+}
+
+void ImageDecodeController::SubtractLayerUsedCount(int layer_id) {
+  if (--used_layer_counts_[layer_id])
+    return;
+
+  // Clean up decode tasks once a layer is no longer used.
+  used_layer_counts_.erase(layer_id);
+  image_decode_tasks_.erase(layer_id);
+}
+
+void ImageDecodeController::OnImageDecodeTaskCompleted(int layer_id,
+                                                       SkPixelRef* pixel_ref,
+                                                       bool was_canceled) {
+  // If the task has successfully finished, then keep the task until the layer
+  // is no longer in use. This ensures that we only decode a pixel ref once.
+  if (!was_canceled)
+    return;
+
+  // Otherwise, we have to clean up the task so that a new one can be created if
+  // we need to decode the pixel ref again.
+  auto layer_it = image_decode_tasks_.find(layer_id);
+  if (layer_it == image_decode_tasks_.end())
+    return;
+
+  auto& pixel_ref_tasks = layer_it->second;
+  auto task_it = pixel_ref_tasks.find(pixel_ref->getGenerationID());
+  if (task_it == pixel_ref_tasks.end())
+    return;
+  pixel_ref_tasks.erase(task_it);
+}
+
+}  // namespace cc