Add crash keys about field trial shared memory errors.

chrome/common/crash_keys.cc

Index: chrome/common/crash_keys.cc
diff --git a/chrome/common/crash_keys.cc b/chrome/common/crash_keys.cc
index 357a0afdb2047245d3afce5a8ba11ef637e66a6d..834970a14e91e171a8bcb7ed0cd2f554662a9d00 100644
--- a/chrome/common/crash_keys.cc
+++ b/chrome/common/crash_keys.cc
@@ -243,6 +243,10 @@ size_t RegisterChromeCrashKeys() {
     {"engine_params", crash_keys::kMediumSize},
     {"engine1_params", crash_keys::kMediumSize},
     {"engine2_params", crash_keys::kMediumSize},
+
+    // Temporary for http://crbug.com/703649.
+    {"field_trial_shmem_create_error", crash_keys::kSmallSize},
+    {"field_trial_shmem_map_error", crash_keys::kSmallSize},
   };
 
   // This dynamic set of keys is used for sets of key value pairs when gathering