Adding direct access to SkMipMap levels.

src/core/SkMipMap.h

Index: src/core/SkMipMap.h
diff --git a/src/core/SkMipMap.h b/src/core/SkMipMap.h
index fe2018c670ceb83d89bce9f30c159578a7d2e64a..928c12d4369dd0a0e646c0fbe68ee276c373e251 100644
--- a/src/core/SkMipMap.h
+++ b/src/core/SkMipMap.h
@@ -23,12 +23,18 @@ public:
     static SkMipMap* Build(const SkPixmap& src, SkDiscardableFactoryProc);
     static SkMipMap* Build(const SkBitmap& src, SkDiscardableFactoryProc);
 
+    // This function lets you determine how many levels a SkMipMap will have without
+    // creating that mipmap.
+    static int ComputeLevelCount(int baseWidth, int baseHeight);
+
     struct Level {
         SkPixmap    fPixmap;
         SkSize      fScale; // < 1.0
     };
 
     bool extractLevel(const SkSize& scale, Level*) const;
+    int countLevels() const;
+    bool getLevel(int index, Level*) const;
 
 protected:
     void onDataChange(void* oldData, void* newData) override {