cc: Don't perform image analysis if the DisplayItemList has no images.

cc/paint/paint_op_buffer.h

 // 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.
 
 #ifndef CC_PAINT_PAINT_OP_BUFFER_H_
 #define CC_PAINT_PAINT_OP_BUFFER_H_
 
 #include <stdint.h>
 
 #include "base/logging.h"
@@ skipping 74 matching lines @@
   // pointer.
   void Raster(SkCanvas* canvas, const SkMatrix& original_ctm) const;
   bool IsDrawOp() const;
 
   // Only valid for draw ops.
   void RasterWithAlpha(SkCanvas* canvas, uint8_t alpha) const;
 
   int CountSlowPaths() const { return 0; }
   int CountSlowPathsFromFlags() const { return 0; }
 
+  bool HasDiscardableImages() const { return false; }
+  bool HasDiscardableImagesFromFlags() const { return false; }
+
   // Returns the number of bytes used by this op in referenced sub records
   // and display lists.  This doesn't count other objects like paths or blobs.
   size_t AdditionalBytesUsed() const { return 0; }
 
   static constexpr bool kIsDrawOp = false;
   static constexpr bool kHasPaintFlags = false;
   static SkRect kUnsetRect;
 };
 
 struct CC_PAINT_EXPORT PaintOpWithFlags : PaintOp {
   static constexpr bool kHasPaintFlags = true;
 
   explicit PaintOpWithFlags(const PaintFlags& flags) : flags(flags) {}
 
   int CountSlowPathsFromFlags() const { return flags.getPathEffect() ? 1 : 0; }
+  bool HasDiscardableImagesFromFlags() const {
+    if (!IsDrawOp())
+      return false;
+
+    SkShader* shader = flags.getShader();
+    SkImage* image = shader ? shader->isAImage(nullptr, nullptr) : nullptr;
+    return image && image->isLazyGenerated();
+  }
 
   // Subclasses should provide a static RasterWithFlags() method which is called
   // from the Raster() method. The RasterWithFlags() should use the PaintFlags
   // passed to it, instead of the |flags| member directly, as some callers may
   // provide a modified PaintFlags. The RasterWithFlags() method is static with
   // a const PaintOpWithFlags* parameter so that it can be used as a function
   // pointer.
   PaintFlags flags;
 };
 
@@ skipping 237 matching lines @@
   // Windows wants to generate these when types are exported, so
   // provide them here explicitly so that DisplayItemList doesn't have
   // to be defined in this header.
   DrawDisplayItemListOp(const DrawDisplayItemListOp& op);
   DrawDisplayItemListOp& operator=(const DrawDisplayItemListOp& op);
   ~DrawDisplayItemListOp();
   static void Raster(const PaintOp* op,
                      SkCanvas* canvas,
                      const SkMatrix& original_ctm);
   size_t AdditionalBytesUsed() const;
+  bool HasDiscardableImages() const;
   // TODO(enne): DisplayItemList should know number of slow paths.
 
   scoped_refptr<DisplayItemList> list;
 };
 
 struct CC_PAINT_EXPORT DrawDRRectOp final : PaintOpWithFlags {
   static constexpr PaintOpType kType = PaintOpType::DrawDRRect;
   static constexpr bool kIsDrawOp = true;
   DrawDRRectOp(const SkRRect& outer,
                const SkRRect& inner,
@@ skipping 25 matching lines @@
   static void Raster(const PaintOp* op,
                      SkCanvas* canvas,
                      const SkMatrix& original_ctm) {
     auto* flags_op = static_cast<const PaintOpWithFlags*>(op);
     RasterWithFlags(flags_op, &flags_op->flags, canvas, original_ctm);
   }
   static void RasterWithFlags(const PaintOpWithFlags* op,
                               const PaintFlags* flags,
                               SkCanvas* canvas,
                               const SkMatrix& original_ctm);
+  bool HasDiscardableImages() const;
 
   PaintImage image;
   SkScalar left;
   SkScalar top;
 };
 
 struct CC_PAINT_EXPORT DrawImageRectOp final : PaintOpWithFlags {
   static constexpr PaintOpType kType = PaintOpType::DrawImageRect;
   static constexpr bool kIsDrawOp = true;
   DrawImageRectOp(const PaintImage& image,
                   const SkRect& src,
                   const SkRect& dst,
                   const PaintFlags* flags,
                   PaintCanvas::SrcRectConstraint constraint);
   ~DrawImageRectOp();
   static void Raster(const PaintOp* op,
                      SkCanvas* canvas,
                      const SkMatrix& original_ctm) {
     auto* flags_op = static_cast<const PaintOpWithFlags*>(op);
     RasterWithFlags(flags_op, &flags_op->flags, canvas, original_ctm);
   }
   static void RasterWithFlags(const PaintOpWithFlags* op,
                               const PaintFlags* flags,
                               SkCanvas* canvas,
                               const SkMatrix& original_ctm);
+  bool HasDiscardableImages() const;
 
   PaintImage image;
   SkRect src;
   SkRect dst;
   PaintCanvas::SrcRectConstraint constraint;
 };
 
 struct CC_PAINT_EXPORT DrawIRectOp final : PaintOpWithFlags {
   static constexpr PaintOpType kType = PaintOpType::DrawIRect;
   static constexpr bool kIsDrawOp = true;
@@ skipping 104 matching lines @@
 
 struct CC_PAINT_EXPORT DrawRecordOp final : PaintOp {
   static constexpr PaintOpType kType = PaintOpType::DrawRecord;
   static constexpr bool kIsDrawOp = true;
   explicit DrawRecordOp(sk_sp<const PaintRecord> record);
   ~DrawRecordOp();
   static void Raster(const PaintOp* op,
                      SkCanvas* canvas,
                      const SkMatrix& original_ctm);
   size_t AdditionalBytesUsed() const;
+  bool HasDiscardableImages() const;
 
   sk_sp<const PaintRecord> record;
 };
 
 struct CC_PAINT_EXPORT DrawRectOp final : PaintOpWithFlags {
   static constexpr PaintOpType kType = PaintOpType::DrawRect;
   static constexpr bool kIsDrawOp = true;
   DrawRectOp(const SkRect& rect, const PaintFlags& flags)
       : PaintOpWithFlags(flags), rect(rect) {}
   static void Raster(const PaintOp* op,
@@ skipping 193 matching lines @@
 
   void playback(SkCanvas* canvas) const;
   void playback(SkCanvas* canvas, SkPicture::AbortCallback* callback) const;
 
   // TODO(enne): These are no longer approximate.  Rename these.
   int approximateOpCount() const { return op_count_; }
   size_t approximateBytesUsed() const {
     return sizeof(*this) + reserved_ + subrecord_bytes_used_;
   }
   int numSlowPaths() const { return num_slow_paths_; }
+  bool HasDiscardableImages() const { return has_discardable_images_; }
 
   // Resize the PaintOpBuffer to exactly fit the current amount of used space.
   void ShrinkToFit();
 
   const SkRect& cullRect() const { return cull_rect_; }
 
   PaintOp* GetFirstOp() const {
     return const_cast<PaintOp*>(first_op_.data_as<PaintOp>());
   }
 
@@ skipping 142 matching lines @@
     op->skip = skip;
     AnalyzeAddedOp(op);
     return op;
   }
 
   template <typename T>
   void AnalyzeAddedOp(const T* op) {
     num_slow_paths_ += op->CountSlowPathsFromFlags();
     num_slow_paths_ += op->CountSlowPaths();
 
+    has_discardable_images_ |= op->HasDiscardableImages();
+    has_discardable_images_ |= op->HasDiscardableImagesFromFlags();
+
     subrecord_bytes_used_ += op->AdditionalBytesUsed();
   }
 
   // As a performance optimization because n=1 is an extremely common case just
   // store the first op in the PaintOpBuffer itself to avoid an extra alloc.
   base::AlignedMemory<sizeof(LargestPaintOp), PaintOpAlign> first_op_;
   std::unique_ptr<char, base::AlignedFreeDeleter> data_;
   size_t used_ = 0;
   size_t reserved_ = 0;
   int op_count_ = 0;
 
   // Record paths for veto-to-msaa for gpu raster.
   int num_slow_paths_ = 0;
   // Record additional bytes used by referenced sub-records and display lists.
   size_t subrecord_bytes_used_ = 0;
+  bool has_discardable_images_ = false;
   SkRect cull_rect_;
 
   DISALLOW_COPY_AND_ASSIGN(PaintOpBuffer);
 };
 
 }  // namespace cc
 
 #endif  // CC_PAINT_PAINT_OP_BUFFER_H_