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

src/gpu/GrLayerAtlas.cpp

Index: src/gpu/GrLayerAtlas.cpp
diff --git a/src/gpu/GrLayerAtlas.cpp b/src/gpu/GrLayerAtlas.cpp
index 3b30607c8cfc72cea328bbea9eb3023b89842098..9beb509f86ebe0e3f51a68de36ce30e10376ab7f 100644
--- a/src/gpu/GrLayerAtlas.cpp
+++ b/src/gpu/GrLayerAtlas.cpp
@@ -6,6 +6,7 @@
  * found in the LICENSE file.
  */
 
+#include "GrGpuResourcePriv.h"
 #include "GrLayerAtlas.h"
 #include "GrRectanizer.h"
 #include "GrTextureProvider.h"
@@ -43,6 +44,32 @@ void GrLayerAtlas::Plot::reset() {
 }
 
 ///////////////////////////////////////////////////////////////////////////////
+GR_DECLARE_STATIC_UNIQUE_KEY(gLayerAtlasKey);
+static const GrUniqueKey& get_layer_atlas_key() {
+    GR_DEFINE_STATIC_UNIQUE_KEY(gLayerAtlasKey);
+    return gLayerAtlasKey;
+}
+
+bool GrLayerAtlas::reattachBackingTexture() {
+    SkASSERT(!fTexture);
+
+    fTexture.reset(fTexProvider->findAndRefTextureByUniqueKey(get_layer_atlas_key()));
+    return SkToBool(fTexture);
+}
+
+void GrLayerAtlas::createBackingTexture() {
+    SkASSERT(!fTexture);
+
+    GrSurfaceDesc desc;
+    desc.fFlags = fFlags;
+    desc.fWidth = fBackingTextureSize.width();
+    desc.fHeight = fBackingTextureSize.height();
+    desc.fConfig = fPixelConfig;
+
+    fTexture.reset(fTexProvider->createTexture(desc, true, nullptr, 0));
+
+    fTexture->resourcePriv().setUniqueKey(get_layer_atlas_key());
+}
 
 GrLayerAtlas::GrLayerAtlas(GrTextureProvider* texProvider, GrPixelConfig config, 
                            GrSurfaceFlags flags,
@@ -52,7 +79,6 @@ GrLayerAtlas::GrLayerAtlas(GrTextureProvider* texProvider, GrPixelConfig config,
     fPixelConfig = config;
     fFlags = flags;
     fBackingTextureSize = backingTextureSize;
-    fTexture = nullptr;
 
     int textureWidth = fBackingTextureSize.width();
     int textureHeight = fBackingTextureSize.height();
@@ -81,8 +107,14 @@ GrLayerAtlas::GrLayerAtlas(GrTextureProvider* texProvider, GrPixelConfig config,
     }
 }
 
+void GrLayerAtlas::resetPlots() {
+    PlotIter iter;
+    for (Plot* plot = iter.init(fPlotList, PlotIter::kHead_IterStart); plot; plot = iter.next()) {
+        plot->reset();
+    }
+}
+
 GrLayerAtlas::~GrLayerAtlas() {
-    SkSafeUnref(fTexture);
     delete[] fPlotArray;
 }
 
@@ -111,14 +143,7 @@ GrLayerAtlas::Plot* GrLayerAtlas::addToAtlas(ClientPlotUsage* usage,
 
     // before we get a new plot, make sure we have a backing texture
     if (nullptr == fTexture) {
-        // TODO: Update this to use the cache rather than directly creating a texture.
-        GrSurfaceDesc desc;
-        desc.fFlags = fFlags;
-        desc.fWidth = fBackingTextureSize.width();
-        desc.fHeight = fBackingTextureSize.height();
-        desc.fConfig = fPixelConfig;
-
-        fTexture = fTexProvider->createTexture(desc, true, nullptr, 0);
+        this->createBackingTexture();
         if (nullptr == fTexture) {
             return nullptr;
         }