unsigned -> int for counts and indices in picture-related code

also, (C)

BUG=skia:

Review URL: https://codereview.chromium.org/1300163002
diff --git a/src/gpu/GrLayerCache.cpp b/src/gpu/GrLayerCache.cpp
index 4d5f2b4..4a20607 100644
--- a/src/gpu/GrLayerCache.cpp
+++ b/src/gpu/GrLayerCache.cpp
@@ -128,7 +128,7 @@
                                          const SkIRect& srcIR,
                                          const SkIRect& dstIR,
                                          const SkMatrix& initialMat,
-                                         const unsigned* key,
+                                         const int* key,
                                          int keySize,
                                          const SkPaint* paint) {
     SkASSERT(pictureID != SK_InvalidGenID && start >= 0 && stop > 0);
@@ -141,7 +141,7 @@
 }
 
 GrCachedLayer* GrLayerCache::findLayer(uint32_t pictureID, const SkMatrix& initialMat,
-                                       const unsigned* key, int keySize) {
+                                       const int* key, int keySize) {
     SkASSERT(pictureID != SK_InvalidGenID);
     return fLayerHash.find(GrCachedLayer::Key(pictureID, initialMat, key, keySize));
 }
@@ -151,7 +151,7 @@
                                                const SkIRect& srcIR,
                                                const SkIRect& dstIR,
                                                const SkMatrix& initialMat,
-                                               const unsigned* key,
+                                               const int* key,
                                                int keySize,
                                                const SkPaint* paint) {
     SkASSERT(pictureID != SK_InvalidGenID && start >= 0 && stop > 0);
@@ -216,7 +216,7 @@
                 pictInfo->incPlotUsage(plot->id());
 #endif
                 // The layer was successfully added to the atlas
-                const SkIRect bounds = SkIRect::MakeXYWH(loc.fX, loc.fY, 
+                const SkIRect bounds = SkIRect::MakeXYWH(loc.fX, loc.fY,
                                                          desc.fWidth, desc.fHeight);
                 layer->setTexture(fAtlas->getTexture(), bounds);
                 layer->setPlot(plot);