Return a Vector instead of a pointer to one from PictureSnapshot::Replay.

For consistency and efficiency.

While here, move the StringBuilder::ReserveCapacity call at the use before the
actual usage of the StringBuilder (presently it has no effect).

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I197140cc0b77d12bd236e908e844eacf39fa6697
Reviewed-on: https://chromium-review.googlesource.com/1106605Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568828}

third_party/blink/renderer/core/inspector/inspector_layer_tree_agent.cc

@@ -522,14 +522,15 @@ Response InspectorLayerTreeAgent::replaySnapshot(const String& snapshot_id,
   Response response = GetSnapshotById(snapshot_id, snapshot);
   if (!response.isSuccess())
     return response;
-  std::unique_ptr<Vector<char>> base64_data = snapshot->Replay(
+  Vector<char> base64_data = snapshot->Replay(
       from_step.fromMaybe(0), to_step.fromMaybe(0), scale.fromMaybe(1.0));
-  if (!base64_data)
+  if (base64_data.IsEmpty())
     return Response::Error("Image encoding failed");
+  static constexpr char kUrlPrefix[] = "data:image/png;base64,";
   StringBuilder url;
-  url.Append("data:image/png;base64,");
-  url.ReserveCapacity(url.length() + base64_data->size());
-  url.Append(base64_data->begin(), base64_data->size());
+  url.ReserveCapacity(sizeof(kUrlPrefix) + base64_data.size());
+  url.Append(kUrlPrefix);
+  url.Append(base64_data.begin(), base64_data.size());
   *data_url = url.ToString();
   return Response::OK();
 }

third_party/blink/renderer/platform/graphics/picture_snapshot.cc

@@ -88,7 +88,7 @@ bool PictureSnapshot::IsEmpty() const {
   return picture_->cullRect().isEmpty();
 }
 
-std::unique_ptr<Vector<char>> PictureSnapshot::Replay(unsigned from_step,
+Vector<char> PictureSnapshot::Replay(unsigned from_step,
                                      unsigned to_step,
                                      double scale) const {
   const SkIRect bounds = picture_->cullRect().roundOut();
@@ -113,7 +113,7 @@ std::unique_ptr<Vector<char>> PictureSnapshot::Replay(unsigned from_step,
     canvas.ResetStepCount();
     picture_->playback(&canvas, &canvas);
   }
-  std::unique_ptr<Vector<char>> base64_data = std::make_unique<Vector<char>>();
+  Vector<char> base64_data;
   Vector<char> encoded_image;
 
   SkPixmap src;
@@ -127,10 +127,10 @@ std::unique_ptr<Vector<char>> PictureSnapshot::Replay(unsigned from_step,
   if (!ImageEncoder::Encode(
           reinterpret_cast<Vector<unsigned char>*>(&encoded_image), src,
           options)) {
-    return nullptr;
+    return Vector<char>();
   }
 
-  Base64Encode(encoded_image, *base64_data);
+  Base64Encode(encoded_image, base64_data);
   return base64_data;
 }
 

third_party/blink/renderer/platform/graphics/picture_snapshot.h

@@ -60,7 +60,7 @@ class PLATFORM_EXPORT PictureSnapshot : public RefCounted<PictureSnapshot> {
 
   PictureSnapshot(sk_sp<const SkPicture>);
 
-  std::unique_ptr<Vector<char>> Replay(unsigned from_step = 0,
+  Vector<char> Replay(unsigned from_step = 0,
                       unsigned to_step = 0,
                       double scale = 1.0) const;
   Vector<Vector<TimeDelta>> Profile(unsigned min_iterations,