Lazily create the Path in StylePath

Instead of creating the Path object up front - when the StylePath is
created - create it on first access/use (usually on paint/layout.)

Review URL: https://codereview.chromium.org/1640313002

Cr-Commit-Position: refs/heads/master@{#371850}

third_party/WebKit/Source/core/style/StylePath.cpp

@@ -7,6 +7,7 @@
 #include "core/css/CSSPathValue.h"
 #include "core/svg/SVGPathByteStream.h"
 #include "core/svg/SVGPathUtilities.h"
+#include "platform/graphics/Path.h"
 
 namespace blink {
 
@@ -14,7 +15,6 @@ StylePath::StylePath(PassRefPtr<SVGPathByteStream> pathByteStream)
     : m_byteStream(pathByteStream)
 {
     ASSERT(m_byteStream);
-    buildPathFromByteStream(*m_byteStream, m_path);
 }
 
 StylePath::~StylePath()
@@ -32,6 +32,15 @@ StylePath* StylePath::emptyPath()
     return emptyPath;
 }
 
+const Path& StylePath::path() const
+{
+    if (!m_path) {
+        m_path = adoptPtr(new Path);
+        buildPathFromByteStream(*m_byteStream, *m_path);
+    }
+    return *m_path;
+}
+
 const SVGPathByteStream& StylePath::byteStream() const
 {
     return *m_byteStream;

third_party/WebKit/Source/core/style/StylePath.h

@@ -5,8 +5,8 @@
 #ifndef StylePath_h
 #define StylePath_h
 
-#include "platform/graphics/Path.h"
 #include "platform/heap/Handle.h"
+#include "wtf/OwnPtr.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
 #include "wtf/RefPtr.h"
@@ -14,6 +14,7 @@
 namespace blink {
 
 class CSSValue;
+class Path;
 class SVGPathByteStream;
 
 class StylePath : public RefCounted<StylePath> {
@@ -23,7 +24,7 @@ public:
 
     static StylePath* emptyPath();
 
-    const Path& path() const { return m_path; }
+    const Path& path() const;
     const SVGPathByteStream& byteStream() const;
 
     PassRefPtrWillBeRawPtr<CSSValue> computedCSSValue() const;
@@ -34,7 +35,7 @@ private:
     explicit StylePath(PassRefPtr<SVGPathByteStream>);
 
     RefPtr<SVGPathByteStream> m_byteStream;
-    Path m_path;
+    mutable OwnPtr<Path> m_path;
 };
 
 } // namespace blink