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..2bf608438598484126522d7c3a2a7652720d9b3e 100644
--- a/src/lazy/SkDiscardablePixelRef.cpp
+++ b/src/lazy/SkDiscardablePixelRef.cpp
@@ -60,15 +60,25 @@ 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;
     }
 
+    if (colorCount > 0) {
+        fCTable.reset(SkNEW_ARGS(SkColorTable, (colors, colorCount)));
+    } else {
+        fCTable.reset(NULL);
+    }
+
     rec->fPixels = pixels;
-    rec->fColorTable = NULL;
+    rec->fColorTable = fCTable.get();

[scroggo, 2014/05/28 15:01:37]

This version does not purge the color table on memory pressure, but maybe that's
okay (it's pretty small, after all).

One way to purge would be to request a larger block of discardable memory and
allocate the color table there. The downside is that someone could take a
reference to it (weren't you interested in removing its inheritance from
SkRefCnt?), and then we might delete/overwrite it underneath them.

[reed1, 2014/05/28 15:48:02]

Agreed, I don't know how to ram the colortable into the discardable block yet,
so that part is not "discardable". I'll add a comment acknowledging this.

     rec->fRowBytes = fRowBytes;
     return true;
 }