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

cc/paint/paint_op_buffer.h

Index: cc/paint/paint_op_buffer.h
diff --git a/cc/paint/paint_op_buffer.h b/cc/paint/paint_op_buffer.h
index fb3518b9d92f112a09748cc3db5f2047a2059958..1018b66069d068bc08966e622a718fd9ea312001 100644
--- a/cc/paint/paint_op_buffer.h
+++ b/cc/paint/paint_op_buffer.h
@@ -85,6 +85,7 @@ struct CC_PAINT_EXPORT PaintOp {
   void RasterWithAlpha(SkCanvas* canvas, uint8_t alpha) const;
 
   int CountSlowPaths() const { return 0; }
+  bool HasDiscardableImages() 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.
@@ -281,6 +282,7 @@ struct CC_PAINT_EXPORT DrawDisplayItemListOp final : PaintOp {
   ~DrawDisplayItemListOp();
   void Raster(SkCanvas* canvas) const;
   size_t AdditionalBytesUsed() const;
+  bool HasDiscardableImages() const;
   // TODO(enne): DisplayItemList should know number of slow paths.
 
   scoped_refptr<DisplayItemList> list;
@@ -311,6 +313,7 @@ struct CC_PAINT_EXPORT DrawImageOp final : PaintOp {
               const PaintFlags* flags);
   ~DrawImageOp();
   void RasterWithFlags(SkCanvas* canvas, const PaintFlags& flags) const;
+  bool HasDiscardableImages() const;
 
   PaintImage image;
   SkScalar left;
@@ -329,6 +332,7 @@ struct CC_PAINT_EXPORT DrawImageRectOp final : PaintOp {
                   PaintCanvas::SrcRectConstraint constraint);
   ~DrawImageRectOp();
   void RasterWithFlags(SkCanvas* canvas, const PaintFlags& flags) const;
+  bool HasDiscardableImages() const;
 
   PaintImage image;
   PaintFlags flags;
@@ -412,6 +416,7 @@ struct CC_PAINT_EXPORT DrawRecordOp final : PaintOp {
   ~DrawRecordOp();
   void Raster(SkCanvas* canvas) const;
   size_t AdditionalBytesUsed() const;
+  bool HasDiscardableImages() const;
 
   sk_sp<const PaintRecord> record;
 };
@@ -570,6 +575,7 @@ class CC_PAINT_EXPORT PaintOpBuffer : public SkRefCnt {
     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();
@@ -721,6 +727,23 @@ class CC_PAINT_EXPORT PaintOpBuffer : public SkRefCnt {
     static int Count(const T* op) { return op->flags.getPathEffect() ? 1 : 0; }
   };
 
+  template <typename T, bool HasFlags>
+  struct HasDiscardableImagesFromFlags {
+    static bool HasDiscardableImages(const T* op) { return false; }
+  };
+
+  template <typename T>
+  struct HasDiscardableImagesFromFlags<T, true> {
+    static bool HasDiscardableImages(const T* op) {
+      if (!op->kIsDrawOp)
+        return false;
+
+      SkShader* shader = op->flags.getShader();
+      SkImage* image = shader ? shader->isAImage(nullptr, nullptr) : nullptr;
+      return image ? image->isLazyGenerated() : false;

[vmpstr, 2017/04/25 17:43:40]

return image && image->isLazyGenerated();

+    }
+  };
+
   template <typename T, typename... Args>
   T* push_internal(size_t bytes, Args&&... args) {
     size_t skip = SkAlignPtr(sizeof(T) + bytes);
@@ -745,6 +768,7 @@ class CC_PAINT_EXPORT PaintOpBuffer : public SkRefCnt {
           op->type = static_cast<uint32_t>(T::kType);
           op->skip = 0;
           op_count_++;
+          AnalyzeAddedOp(op);
           return op;
         }
       }
@@ -763,13 +787,20 @@ class CC_PAINT_EXPORT PaintOpBuffer : public SkRefCnt {
     op->type = static_cast<uint32_t>(T::kType);
     op->skip = skip;
     op_count_++;
+    AnalyzeAddedOp(op);
+    return op;
+  }
 
+  template <typename T>
+  void AnalyzeAddedOp(const T* op) {
     num_slow_paths_ += CountSlowPathsFromFlags<T, T::kHasPaintFlags>::Count(op);
     num_slow_paths_ += op->CountSlowPaths();
 
-    subrecord_bytes_used_ += op->AdditionalBytesUsed();
+    has_discardable_images_ |= op->HasDiscardableImages();
+    has_discardable_images_ |= HasDiscardableImagesFromFlags<
+        T, T::kHasPaintFlags>::HasDiscardableImages(op);
 
-    return op;
+    subrecord_bytes_used_ += op->AdditionalBytesUsed();
   }
 
   // As a performance optimization because n=1 is an extremely common case just
@@ -785,6 +816,7 @@ class CC_PAINT_EXPORT PaintOpBuffer : public SkRefCnt {
   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);