Update SkLightingShader to support rotation

src/core/SkLight.h

+
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkLight_DEFINED
+#define SkLight_DEFINED
+
+#include "SkPoint3.h"
+
+class SK_API SkLight {
+public:
+    enum LightType {
+        kAmbient_LightType,       // only 'fColor' is used
+        kDirectional_LightType
+    };
+
+    SkLight() : fType(kAmbient_LightType) {
+        fColor.set(0.0f, 0.0f, 0.0f);
+        fDirection.set(0.0f, 0.0f, 1.0f);
+    }
+
+    SkLight(const SkColor3f& color)
+        : fType(kAmbient_LightType)
+        , fColor(color) {
+        fDirection.set(0.0f, 0.0f, 1.0f);
+    }
+
+    SkLight(const SkColor3f& color, const SkVector3& dir)
+        : fType(kDirectional_LightType)
+        , fColor(color)
+        , fDirection(dir) {
+        if (!fDirection.normalize()) {
+            fDirection.set(0.0f, 0.0f, 1.0f);
+        }
+    }
+
+    LightType type() const { return fType; }
+    const SkColor3f& color() const { return fColor; }
+    const SkVector3& dir() const { 
+        SkASSERT(kAmbient_LightType != fType);
+        return fDirection; 
+    }
+
+private:
+    LightType   fType;
+    SkColor3f   fColor;           // linear (unpremul) color. Range is 0..1 in each channel.
+    SkVector3   fDirection;       // direction towards the light (+Z is out of the screen).
+                                  // If degenerate, it will be replaced with (0, 0, 1).
+};
+
+
+#endif