Switch out random number generator for tests, benches, samples.

This change makes tests, benches and samples use the new SkMWCRandom PRNG. GMs will be saved for another time, as they'll require rebaselining.

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

Author: jvanverth@google.com

Review URL: https://chromiumcodereview.appspot.com/23653018

git-svn-id: http://skia.googlecode.com/svn/trunk@11136 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tests/MathTest.cpp b/tests/MathTest.cpp
index fe54594..5ec91a9 100644
--- a/tests/MathTest.cpp
+++ b/tests/MathTest.cpp
@@ -19,7 +19,7 @@
     REPORTER_ASSERT(reporter, 1 == SkCLZ(1 << 30));
     REPORTER_ASSERT(reporter, 0 == SkCLZ(~0U));
 
-    SkRandom rand;
+    SkMWCRandom rand;
     for (int i = 0; i < 1000; ++i) {
         uint32_t mask = rand.nextU();
         // need to get some zeros for testing, but in some obscure way so the
@@ -82,7 +82,7 @@
     }
 #endif
 
-    SkRandom rand;
+    SkMWCRandom rand;
     for (int i = 0; i < 10000; ++i) {
         unsigned a = rand.nextU() & 0x7FFF;
         unsigned b = rand.nextU() & 0x7FFF;