[SVGDom] Initial linear gradient support

experimental/svg/model/SkSVGRenderContext.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkSVGRenderContext_DEFINED
 #define SkSVGRenderContext_DEFINED
 
 #include "SkPaint.h"
 #include "SkRect.h"
 #include "SkSize.h"
 #include "SkSVGAttribute.h"
+#include "SkSVGIDMapper.h"
 #include "SkTLazy.h"
 #include "SkTypes.h"
 
 class SkCanvas;
 class SkSVGLength;
 
 class SkSVGLengthContext {
 public:
     SkSVGLengthContext(const SkSize& viewport, SkScalar dpi = 90)
         : fViewport(viewport), fDPI(dpi) {}
@@ skipping 24 matching lines @@
     // Inherited presentation attributes, computed for the current node.
     SkSVGPresentationAttributes fInherited;
 
     // Cached paints, reflecting the current presentation attributes.
     SkPaint fFillPaint;
     SkPaint fStrokePaint;
 };
 
 class SkSVGRenderContext {
 public:
-    SkSVGRenderContext(SkCanvas*, const SkSVGLengthContext&, const SkSVGPresentationContext&);
+    SkSVGRenderContext(SkCanvas*, const SkSVGIDMapper&, const SkSVGLengthContext&,
+                       const SkSVGPresentationContext&);
     SkSVGRenderContext(const SkSVGRenderContext&);
     ~SkSVGRenderContext();
 
     const SkSVGLengthContext& lengthContext() const { return *fLengthContext; }
     SkSVGLengthContext* writableLengthContext() { return fLengthContext.writable(); }
 
     SkCanvas* canvas() const { return fCanvas; }
 
     void applyPresentationAttributes(const SkSVGPresentationAttributes&);
 
+    const SkSVGNode* findNodeById(const SkString&) const;
+
     const SkPaint* fillPaint() const;
     const SkPaint* strokePaint() const;
 
 private:
     // Stack-only
     void* operator new(size_t)                               = delete;
     void* operator new(size_t, void*)                        = delete;
     SkSVGRenderContext& operator=(const SkSVGRenderContext&) = delete;
 
+    const SkSVGIDMapper&                          fIDMapper;
     SkTCopyOnFirstWrite<SkSVGLengthContext>       fLengthContext;
     SkTCopyOnFirstWrite<SkSVGPresentationContext> fPresentationContext;
     SkCanvas*                                     fCanvas;
     // The save count on 'fCanvas' at construction time.
     // A restoreToCount() will be issued on destruction.
     int                                           fCanvasSaveCount;
 };
 
 #endif // SkSVGRenderContext_DEFINED