add colortable support to imagegenerator

src/lazy/SkDiscardablePixelRef.cpp

Index: src/lazy/SkDiscardablePixelRef.cpp
diff --git a/src/lazy/SkDiscardablePixelRef.cpp b/src/lazy/SkDiscardablePixelRef.cpp
index ccf812ce6f7a6a13619645d16adb9e9b374cc675..b0bbd27e3a5f5473b541a68f94f1f61792c67017 100644
--- a/src/lazy/SkDiscardablePixelRef.cpp
+++ b/src/lazy/SkDiscardablePixelRef.cpp
@@ -60,15 +60,30 @@ bool SkDiscardablePixelRef::onNewLockPixels(LockRec* rec) {
     }
 
     void* pixels = fDiscardableMemory->data();
-    if (!fGenerator->getPixels(this->info(), pixels, fRowBytes)) {
+    const SkImageInfo& info = this->info();
+    SkPMColor colors[256];
+    int colorCount = 0;
+
+    if (!fGenerator->getPixels(info, pixels, fRowBytes, colors, &colorCount)) {
         fDiscardableMemory->unlock();
         SkDELETE(fDiscardableMemory);
         fDiscardableMemory = NULL;
         return false;
     }
 
+    // Note: our ctable is not purgable, as it is not stored in the discardablememory block.
+    // This is because SkColorTable is refcntable, and therefore our caller could hold onto it
+    // beyond the scope of a lock/unlock. If we change the API/lifecycle for SkColorTable, we
+    // could move it into the block, but then again perhaps it is small enough that this doesn't
+    // really matter.
+    if (colorCount > 0) {
+        fCTable.reset(SkNEW_ARGS(SkColorTable, (colors, colorCount)));
+    } else {
+        fCTable.reset(NULL);
+    }
+
     rec->fPixels = pixels;
-    rec->fColorTable = NULL;
+    rec->fColorTable = fCTable.get();
     rec->fRowBytes = fRowBytes;
     return true;
 }