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

The goal here is to get people to start using the new random number
generator, while leaving the old one in place so we don't have to 
rebaseline GMs.

R=reed@google.com, bsalomon@google.com

Author: jvanverth@google.com

Review URL: https://chromiumcodereview.appspot.com/23576015

git-svn-id: http://skia.googlecode.com/svn/trunk@11169 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tests/PackBitsTest.cpp b/tests/PackBitsTest.cpp
index 59c8a8c..f7d4b8e 100644
--- a/tests/PackBitsTest.cpp
+++ b/tests/PackBitsTest.cpp
@@ -14,7 +14,7 @@
 static const uint16_t gTest3[] = { 0, 0, 0, 0, 0, 0, 1, 2, 3, 3, 3, 0, 0, 1 };
 
 #include "SkRandom.h"
-static SkMWCRandom gRand;
+static SkRandom gRand;
 static void rand_fill(uint16_t buffer[], int count) {
     for (int i = 0; i < count; i++)
         buffer[i] = (uint16_t)gRand.nextU();