ensure 4-byte alignment for storage, as SkWriterBuffer requires it

tests/ImageIsOpaqueTest.cpp

Index: tests/ImageIsOpaqueTest.cpp
diff --git a/tests/ImageIsOpaqueTest.cpp b/tests/ImageIsOpaqueTest.cpp
index 6fdbc8127abf4a4165c238393771af29f5cd78bd..6d886d48bfb19e05b40cb4e8f5dab86f58dcea24 100644
--- a/tests/ImageIsOpaqueTest.cpp
+++ b/tests/ImageIsOpaqueTest.cpp
@@ -17,8 +17,8 @@
 #include "SkWriteBuffer.h"
 
 static void test_flatten(skiatest::Reporter* reporter, const SkImageInfo& info) {
-    // just need a safe amount of storage
-    char storage[sizeof(SkImageInfo)*2];
+    // just need a safe amount of storage, but ensure that it is 4-byte aligned.
+    int32_t storage[(sizeof(SkImageInfo)*2) / sizeof(int32_t)];
     SkWriteBuffer wb(storage, sizeof(storage));
     info.flatten(wb);
     SkASSERT(wb.bytesWritten() < sizeof(storage));