Use SkPathRef gen id for SkPath::getGenerationID

include/core/SkPathRef.h

Index: include/core/SkPathRef.h
diff --git a/include/core/SkPathRef.h b/include/core/SkPathRef.h
index d832944ec340a6a04c573aeb029a8ff5c9cc9dfd..399e37e88148f712a840787e247d8a6c6b273806 100644
--- a/include/core/SkPathRef.h
+++ b/include/core/SkPathRef.h
@@ -227,6 +227,14 @@ public:
      */
     uint32_t writeSize();
 
+    /**
+     * Gets an ID that uniquely identifies the contents of the path ref. If two path refs have the
+     * same ID then they have the same verbs and points. However, two path refs may have the same
+     * contents but different genIDs. Zero is reserved and means an ID has not yet been determined

[mtklein, 2013/10/29 20:38:36]

We don't ever return 0 here do we?  Do we need to tell the reader that 0 is
special here?  Or just a simple "Will never return 0."?  I hate to expose why.

[bsalomon, 2013/10/29 20:45:04]

good point, done.

+     * for the path ref.
+     */
+    uint32_t genID() const;
+
 private:
     enum SerializationOffsets {
         kIsFinite_SerializationShift = 25,  // requires 1 bit
@@ -380,14 +388,6 @@ private:
         return reinterpret_cast<intptr_t>(fVerbs) - reinterpret_cast<intptr_t>(fPoints);
     }
 
-    /**
-     * Gets an ID that uniquely identifies the contents of the path ref. If two path refs have the
-     * same ID then they have the same verbs and points. However, two path refs may have the same
-     * contents but different genIDs. Zero is reserved and means an ID has not yet been determined
-     * for the path ref.
-     */
-    int32_t genID() const;
-
     SkDEBUGCODE(void validate() const;)
 
     /**
@@ -413,7 +413,7 @@ private:
     enum {
         kEmptyGenID = 1, // GenID reserved for path ref with zero points and zero verbs.
     };
-    mutable int32_t     fGenerationID;
+    mutable uint32_t    fGenerationID;
     SkDEBUGCODE(int32_t fEditorsAttached;) // assert that only one editor in use at any time.
 
     typedef SkRefCnt INHERITED;