Gradient for VectorDrawable's fill and stroke

Add ComplexColor interface for both GradientColor and ColorStateList.
Set up constant state, factory, theme attrs for GradientColor, while
refactoring the ColorStateList's similar code. (Functionality in CSL should
be the same).

Support themeing in both the root and item level in GradientColor.
For example, both startColor in <gradient> tag or color in <item> tag can
have theme color.
Add tests for both simple and complex cases with themeing etc.

Hook up the native VectorDrawable implementation using 2 extra JNI calls for
simplicity. Such calls only happen at inflate and applyTheme call.

b/22564318

Change-Id: Ibdc564ddb4a7ee0133c6141c4784782f0c93ce0e
diff --git a/libs/hwui/VectorDrawable.h b/libs/hwui/VectorDrawable.h
index 5ae5f6a..09bdce5 100644
--- a/libs/hwui/VectorDrawable.h
+++ b/libs/hwui/VectorDrawable.h
@@ -26,6 +26,7 @@
 #include <SkPath.h>
 #include <SkPathMeasure.h>
 #include <SkRect.h>
+#include <SkShader.h>
 
 #include <cutils/compiler.h>
 #include <stddef.h>
@@ -95,7 +96,7 @@
 protected:
     virtual const SkPath& getUpdatedPath();
     virtual void drawPath(SkCanvas *outCanvas, const SkPath& renderPath,
-            float strokeScale) = 0;
+            float strokeScale, const SkMatrix& matrix) = 0;
     Data mData;
     SkPath mSkPath;
     bool mSkPathDirty = true;
@@ -108,6 +109,11 @@
     FullPath() : Path() {}
     FullPath(const Data& nodes) : Path(nodes) {}
 
+    ~FullPath() {
+        SkSafeUnref(mFillGradient);
+        SkSafeUnref(mStrokeGradient);
+    }
+
     void updateProperties(float strokeWidth, SkColor strokeColor,
             float strokeAlpha, SkColor fillColor, float fillAlpha,
             float trimPathStart, float trimPathEnd, float trimPathOffset,
@@ -162,10 +168,18 @@
     }
     bool getProperties(int8_t* outProperties, int length);
 
+    void setFillGradient(SkShader* fillGradient) {
+        SkRefCnt_SafeAssign(mFillGradient, fillGradient);
+    };
+    void setStrokeGradient(SkShader* strokeGradient) {
+        SkRefCnt_SafeAssign(mStrokeGradient, strokeGradient);
+    };
+
+
 protected:
     const SkPath& getUpdatedPath() override;
     void drawPath(SkCanvas* outCanvas, const SkPath& renderPath,
-            float strokeScale) override;
+            float strokeScale, const SkMatrix& matrix) override;
 
 private:
     // Applies trimming to the specified path.
@@ -174,6 +188,8 @@
     SkColor mStrokeColor = SK_ColorTRANSPARENT;
     float mStrokeAlpha = 1;
     SkColor mFillColor = SK_ColorTRANSPARENT;
+    SkShader* mStrokeGradient = nullptr;
+    SkShader* mFillGradient = nullptr;
     float mFillAlpha = 1;
     float mTrimPathStart = 0;
     float mTrimPathEnd = 1;
@@ -195,7 +211,7 @@
 
 protected:
     void drawPath(SkCanvas* outCanvas, const SkPath& renderPath,
-            float strokeScale) override;
+            float strokeScale, const SkMatrix& matrix) override;
 };
 
 class ANDROID_API Group: public Node {