Change old PRG to be SkLCGRandom; change new one to SkRandom

bench/GrMemoryPoolBench.cpp

Index: bench/GrMemoryPoolBench.cpp
diff --git a/bench/GrMemoryPoolBench.cpp b/bench/GrMemoryPoolBench.cpp
index 78a283b0c52e66c9eb8211b45cac96f94f49474d..dccf8278f541083ffc026c8f95a47791177ba534 100644
--- a/bench/GrMemoryPoolBench.cpp
+++ b/bench/GrMemoryPoolBench.cpp
@@ -47,7 +47,7 @@ protected:
     }
 
     virtual void onDraw(SkCanvas*) {
-        SkMWCRandom r;
+        SkRandom r;
         enum {
             kMaxObjects = 4 * (1 << 10),
         };
@@ -103,7 +103,7 @@ protected:
     }
 
     virtual void onDraw(SkCanvas*) {
-        SkMWCRandom r;
+        SkRandom r;
         enum {
             kMaxObjects = 4 * (1 << 10),
         };
@@ -141,7 +141,7 @@ protected:
     }
 
     virtual void onDraw(SkCanvas*) {
-        SkMWCRandom r;
+        SkRandom r;
         A* objects[M];
         for (int i = 0; i < N; i++) {
             uint32_t count = r.nextRangeU(0, M-1);