simplify uniqueID code in picture

patch from issue 750003002 at patchset 1 (http://crrev.com/750003002#ps1)

BUG=skia:

Review URL: https://codereview.chromium.org/752573002

2 files changed, 22 insertions, 32 deletions

diff --git a/include/core/SkPicture.h b/include/core/SkPicture.h
index dc522a5c9d..e9500b25c5 100644
--- a/include/core/SkPicture.h
+++ b/include/core/SkPicture.h
@@ -128,12 +128,9 @@ public:
     */
     SkRect cullRect() const { return fCullRect; }
 
-    /** Return a non-zero, unique value representing the picture. This call is
-        only valid when not recording. Between a beginRecording/endRecording
-        pair it will just return 0 (the invalid ID). Each beginRecording/
-        endRecording pair will cause a different generation ID to be returned.
-    */
-    uint32_t uniqueID() const;
+    /** Return a non-zero, unique value representing the picture.
+     */
+    uint32_t uniqueID() const { return fUniqueID; }
 
     /**
      *  Function to encode an SkBitmap to an SkData. A function with this
@@ -249,7 +246,6 @@ private:
     static const uint32_t MIN_PICTURE_VERSION = 19;
     static const uint32_t CURRENT_PICTURE_VERSION = 37;
 
-    void needsNewGenID() { fUniqueID = SK_InvalidGenID; }
     void callDeletionListeners();
 
     void createHeader(SkPictInfo* info) const;
@@ -264,12 +260,12 @@ private:
                                    SkPicture const* const drawablePics[], int drawableCount);
 
     // uint32_t fRefCnt; from SkNVRefCnt<SkPicture>
-    mutable uint32_t fUniqueID;
+    const uint32_t                        fUniqueID;
     const SkRect                          fCullRect;
     mutable SkAutoTUnref<const AccelData> fAccelData;
     mutable SkTDArray<DeletionListener*> fDeletionListeners;  // pointers are refed
-    SkAutoTDelete<SkRecord>       fRecord;
-    SkAutoTUnref<SkBBoxHierarchy> fBBH;
+    SkAutoTDelete<const SkRecord>       fRecord;
+    SkAutoTUnref<const SkBBoxHierarchy> fBBH;
     SkAutoTUnref<SkData>          fDrawablePicts;
 
     // helpers for fDrawablePicts
diff --git a/src/core/SkPicture.cpp b/src/core/SkPicture.cpp
index 7f4b33afac..4848345e51 100644
--- a/src/core/SkPicture.cpp
+++ b/src/core/SkPicture.cpp
@@ -45,6 +45,18 @@ template <typename T> int SafeCount(const T* obj) {
     return obj ? obj->count() : 0;
 }
 
+static int32_t gPictureGenerationID;
+
+// never returns a 0
+static int32_t next_picture_generation_id() {
+    // Loop in case our global wraps around.
+    int32_t genID;
+    do {
+        genID = sk_atomic_inc(&gPictureGenerationID) + 1;
+    } while (0 == genID);
+    return genID;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 namespace {
@@ -512,33 +524,15 @@ bool SkPicture::hasText()             const { return fAnalysis.fHasText; }
 bool SkPicture::willPlayBackBitmaps() const { return fAnalysis.fWillPlaybackBitmaps; }
 int  SkPicture::approximateOpCount()  const { return fRecord->count(); }
 
-static int32_t gPictureGenerationID = SK_InvalidGenID;  // This will be set at link time.
-
-static int32_t next_picture_generation_id() {
-    // Loop in case our global wraps around.
-    int32_t genID;
-    do {
-        genID = sk_atomic_inc(&gPictureGenerationID) + 1;
-    } while (SK_InvalidGenID == genID);
-    return genID;
-}
-
-uint32_t SkPicture::uniqueID() const {
-    if (SK_InvalidGenID == fUniqueID) {
-        fUniqueID = next_picture_generation_id();
-    }
-    return fUniqueID;
-}
-
 SkPicture::SkPicture(const SkRect& cullRect, SkRecord* record, SkData* drawablePicts,
                      SkBBoxHierarchy* bbh)
-    : fCullRect(cullRect)
+    : fUniqueID(next_picture_generation_id())
+    , fCullRect(cullRect)
     , fRecord(record)
     , fBBH(SkSafeRef(bbh))
     , fDrawablePicts(SkSafeRef(drawablePicts))
-    , fAnalysis(*fRecord) {
-    this->needsNewGenID();
-}
+    , fAnalysis(*fRecord)
+{}
 
 // Note that we are assuming that this entry point will only be called from
 // one thread. Currently the only client of this method is