Calculate and track display item opaqueness

third_party/WebKit/Source/platform/graphics/paint/PaintChunk.h

 // 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.
 
 #ifndef PaintChunk_h
 #define PaintChunk_h
 
 #include "platform/geometry/FloatRect.h"
 #include "platform/graphics/paint/PaintChunkProperties.h"
 #include "wtf/Allocator.h"
 #include <iosfwd>
 
 namespace blink {
 
 // A contiguous sequence of drawings with common paint properties.
 //
 // This is expected to be owned by the paint artifact which also owns the
 // related drawings.
 //
 // This is a Slimming Paint v2 class.
 struct PaintChunk {
     DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();
-    PaintChunk() : beginIndex(0), endIndex(0) { }
+    PaintChunk() : beginIndex(0), endIndex(0), knownToBeOpaque(false) { }
     PaintChunk(unsigned begin, unsigned end, const PaintChunkProperties& props)
-        : beginIndex(begin), endIndex(end), properties(props) { }
+        : beginIndex(begin), endIndex(end), properties(props), knownToBeOpaque(false) { }
 
     // Index of the first drawing in this chunk.
     unsigned beginIndex;
 
     // Index of the first drawing not in this chunk, so that there are
     // |endIndex - beginIndex| drawings in the chunk.
     unsigned endIndex;
 
     // The paint properties which apply to this chunk.
     PaintChunkProperties properties;
 
     // The total bounds of this paint chunk's contents.
     FloatRect bounds;
+
+    // True if the bounds are filled entirely with opaque contents.
+    bool knownToBeOpaque;
 };
 
 inline bool operator==(const PaintChunk& a, const PaintChunk& b)
 {
     return a.beginIndex == b.beginIndex
         && a.endIndex == b.endIndex
         && a.properties == b.properties
-        && a.bounds == b.bounds;
+        && a.bounds == b.bounds
+        && a.knownToBeOpaque == b.knownToBeOpaque;
 }
 
 inline bool operator!=(const PaintChunk& a, const PaintChunk& b)
 {
     return !(a == b);
 }
 
 // Redeclared here to avoid ODR issues.
 // See platform/testing/PaintPrinters.h.
 void PrintTo(const PaintChunk&, std::ostream*);
 
 } // namespace blink
 
 #endif // PaintChunk_h