net: disable ECDSA ciphersuites on platforms where we can't support it.

net/base/ssl_config_service.h

Index: net/base/ssl_config_service.h
diff --git a/net/base/ssl_config_service.h b/net/base/ssl_config_service.h
index de430e1472804cd23ec56f8c4aa05f7f65fafc09..47b0f9eb0480bb3fe67ea7bc821f8c8ce65e4f28 100644
--- a/net/base/ssl_config_service.h
+++ b/net/base/ssl_config_service.h
@@ -74,6 +74,8 @@ struct NET_EXPORT SSLConfig {
   // - FORTEZZA cipher suites (obsolete).
   // - IDEA cipher suites (RFC 5469 explains why).
   // - Anonymous cipher suites.
+  // - ECDSA cipher suites on platforms where certificate verification cannot
+  //   handle them.
   // The ciphers listed in |disabled_cipher_suites| will be removed in addition
   // to the above list.
   //