Update Layer Hoisting to store its atlas texture in the resource cache

src/gpu/GrLayerCache.h

Index: src/gpu/GrLayerCache.h
diff --git a/src/gpu/GrLayerCache.h b/src/gpu/GrLayerCache.h
index 914d0d5a58c408206529a5b88e47f5f73a2019c1..a606681896621f935147cb85dbbc7561699d57a7 100644
--- a/src/gpu/GrLayerCache.h
+++ b/src/gpu/GrLayerCache.h
@@ -165,6 +165,7 @@ public:
         , fPaint(paint ? new SkPaint(*paint) : nullptr)
         , fFilter(nullptr)
         , fTexture(nullptr)
+        , fAtlased(false)
         , fRect(SkIRect::MakeEmpty())
         , fPlot(nullptr)
         , fUses(0)
@@ -180,7 +181,9 @@ public:
     }
 
     ~GrCachedLayer() {
-        SkSafeUnref(fTexture);
+        if (!fAtlased) {
+            SkSafeUnref(fTexture);
+        }
         SkSafeUnref(fFilter);
         delete fPaint;
     }
@@ -195,8 +198,15 @@ public:
     const SkIRect& srcIR() const { return fSrcIR; }
     const SkIRect& dstIR() const { return fDstIR; }
     int stop() const { return fStop; }
-    void setTexture(GrTexture* texture, const SkIRect& rect) {
-        SkRefCnt_SafeAssign(fTexture, texture);
+    void setTexture(GrTexture* texture, const SkIRect& rect, bool atlased) {
+        if (texture && !atlased) {
+            texture->ref();  // non-atlased textures carry a ref
+        }
+        if (fTexture && !fAtlased) {
+            fTexture->unref();  // non-atlased textures carry a ref
+        }
+        fTexture = texture;
+        fAtlased = atlased;
         fRect = rect;
         if (!fTexture) {
             fLocked = false;
@@ -216,7 +226,7 @@ public:
     }
     GrLayerAtlas::Plot* plot() { return fPlot; }
 
-    bool isAtlased() const { return SkToBool(fPlot); }
+    bool isAtlased() const { SkASSERT(fAtlased == SkToBool(fPlot)); return fAtlased; }
 
     void setLocked(bool locked) { fLocked = locked; }
     bool locked() const { return fLocked; }
@@ -252,6 +262,10 @@ private:
     // ref on a GrTexture for non-atlased textures.
     GrTexture*      fTexture;
 
+    // true if this layer is in the atlas (and 'fTexture' doesn't carry a ref)
+    // and false if the layer is a free floater (and carries a ref).
+    bool            fAtlased;
+
     // For both atlased and non-atlased layers 'fRect' contains the  bound of
     // the layer in whichever texture it resides. It is empty when 'fTexture'
     // is nullptr.
@@ -285,10 +299,9 @@ private:
 // The GrLayerCache caches pre-computed saveLayers for later rendering.
 // Non-atlased layers are stored in their own GrTexture while the atlased
 // layers share a single GrTexture.
-// Unlike the GrFontCache, the GrTexture atlas only has one GrAtlas (for 8888)
-// and one GrPlot (for the entire atlas). As such, the GrLayerCache
-// roughly combines the functionality of the GrFontCache and GrTextStrike
-// classes.
+// Unlike the GrFontCache, the GrLayerCache only has one atlas (for 8888).
+// As such, the GrLayerCache roughly combines the functionality of the
+// GrFontCache and GrTextStrike classes.
 class GrLayerCache {
 public:
     GrLayerCache(GrContext*);
@@ -346,6 +359,9 @@ public:
         return width <= kPlotWidth && height <= kPlotHeight;
     }
 
+    void begin();
+    void end();
+
 #if !GR_CACHE_HOISTED_LAYERS
     void purgeAll();
 #endif
@@ -361,7 +377,7 @@ private:
     static const int kPlotHeight = kAtlasTextureHeight / kNumPlotsY;
 
     GrContext*                  fContext;  // pointer back to owning context
-    SkAutoTDelete<GrLayerAtlas> fAtlas;    // TODO: could lazily allocate
+    SkAutoTDelete<GrLayerAtlas> fAtlas;    // lazily allocated
 
     // We cache this information here (rather then, say, on the owning picture)
     // because we want to be able to clean it up as needed (e.g., if a picture
@@ -397,9 +413,9 @@ private:
 
     void purgePlot(GrLayerAtlas::Plot* plot);
 
-    // Try to find a purgeable plot and clear it out. Return true if a plot
+    // Either purge all un-locked plots or just one. Return true if >= 1 plot
     // was purged; false otherwise.
-    bool purgePlot();
+    bool purgePlots(bool justOne);
 
     void incPlotLock(int plotIdx) { ++fPlotLocks[plotIdx]; }
     void decPlotLock(int plotIdx) {