Add a switch for using PNaCl Subzero and use it for -O0 translation.

components/nacl/browser/pnacl_translation_cache_unittest.cc

Index: components/nacl/browser/pnacl_translation_cache_unittest.cc
diff --git a/components/nacl/browser/pnacl_translation_cache_unittest.cc b/components/nacl/browser/pnacl_translation_cache_unittest.cc
index dcba62f7b61c7d183096e2585e82f7ccc683c9ef..a8c8093a7a7f90d36a0544517b150b2159a084b5 100644
--- a/components/nacl/browser/pnacl_translation_cache_unittest.cc
+++ b/components/nacl/browser/pnacl_translation_cache_unittest.cc
@@ -177,6 +177,13 @@ TEST(PnaclTranslationCacheKeyTest, CacheKeyTest) {
             "modified:1995:11:15:6:25:24:0:UTC;etag:;"
             "sandbox:x86-32;extra_flags:;",
             PnaclTranslationCache::GetKey(info));
+  // Check that Subzero gets a different cache key.
+  info.use_subzero = true;
+  EXPECT_EQ("ABI:2;opt:2subzero;URL:http://www.google.com/;"
+            "modified:1995:11:15:6:25:24:0:UTC;etag:;"
+            "sandbox:x86-32;extra_flags:;",
+            PnaclTranslationCache::GetKey(info));
+  info.use_subzero = false;
   info.etag = std::string("etag");
   EXPECT_EQ("ABI:2;opt:2;URL:http://www.google.com/;"
             "modified:1995:11:15:6:25:24:0:UTC;etag:etag;"