Initialize memory for BitMask and Clip test.

BUG=skia:

Review URL: https://codereview.chromium.org/1466713002
diff --git a/tests/BlitMaskClip.cpp b/tests/BlitMaskClip.cpp
index a3bce17..8ba2cea 100644
--- a/tests/BlitMaskClip.cpp
+++ b/tests/BlitMaskClip.cpp
@@ -8,6 +8,7 @@
 #include "SkBlitter.h"
 #include "SkMask.h"
 #include "Test.h"
+#include <string.h>
 
 class TestBlitter : public SkBlitter {
 public:
@@ -28,7 +29,6 @@
     skiatest::Reporter* fReporter;
 };
 
-
 // Exercise all clips compared with different widths of bitMask. Make sure that no buffer
 // overruns happen.
 DEF_TEST(BlitAndClip, reporter) {
@@ -38,6 +38,7 @@
         const int height = 2;
         int rowBytes = (width + 7) >> 3;
         uint8_t* bits = new uint8_t[rowBytes * height];
+        memset(bits, 0xAA, rowBytes * height);
 
         SkIRect b = {originX, originY, originX + width, originY + height};