Update url_canon_icu prevent crash with GoogleUrl.

url/url_canon_icu.cc

Index: url/url_canon_icu.cc
diff --git a/url/url_canon_icu.cc b/url/url_canon_icu.cc
index 741bed22abf09f0e9b1eb778f67fc3ae155a5ee5..57cc9435a2237384d22f71d3cd158dedb33eec78 100644
--- a/url/url_canon_icu.cc
+++ b/url/url_canon_icu.cc
@@ -163,7 +163,9 @@ bool IDNToASCII(const base::char16* src, int src_len, CanonOutputW* output) {
   DCHECK(output->length() == 0);  // Output buffer is assumed empty.
 
   UIDNA* uidna = g_uidna.Get().value;
-  DCHECK(uidna != NULL);
+  if (uidna == NULL) {
+    return false;  // Prevent null-deref in uidna_nameToASCII.
+  }

[jungshik at Google, 2015/03/27 21:59:16]

This should not happen. If it happens, we have to track down the root cause. 
g_uidna is obtained here and I wonder why uidna_openUTS46 is failing. Is it
failing in Chrome? Moreover, it cannot depend on the input url.  

struct UIDNAWrapper {
  UIDNAWrapper() {
    UErrorCode err = U_ZERO_ERROR;
    // TODO(jungshik): Change options as different parties (browsers,
    // registrars, search engines) converge toward a consensus.
    value = uidna_openUTS46(UIDNA_CHECK_BIDI, &err);
    if (U_FAILURE(err))
      value = NULL;
  }

  UIDNA* value;
};

   while (true) {
     UErrorCode err = U_ZERO_ERROR;
     UIDNAInfo info = UIDNA_INFO_INITIALIZER;