[Sync] Nest UserEvent message classes within UserEventSpecifics.

components/sync/protocol/user_event_specifics.proto

Index: components/sync/protocol/user_event_specifics.proto
diff --git a/components/sync/protocol/user_event_specifics.proto b/components/sync/protocol/user_event_specifics.proto
index a2648f0b9851eed92b8c7a58320580309629f01c..d6a8066ba93eebcb1638d56f464f6152bf5d0ae4 100644
--- a/components/sync/protocol/user_event_specifics.proto
+++ b/components/sync/protocol/user_event_specifics.proto
@@ -13,64 +13,6 @@ option optimize_for = LITE_RUNTIME;
 
 package sync_pb;
 
-message FieldTrial {
-  message FieldTrialPair {
-    optional fixed32 name_id = 1;
-    optional fixed32 group_id = 2;
-  }
-  repeated FieldTrialPair field_trial_pairs = 1;
-}
-
-// Language detection output.
-message LanguageDetection {
-  message Language {
-    // ISO 639 language code will be used.
-    optional string language_code = 1;
-    // Whether the detected language is reliable, note this is determined by
-    // the CLD3.
-    optional bool is_reliable = 2;
-  }
-  // Top n languages. Typically we just log the top language, but for page that
-  // we're not confident about, we may log up to 3 top languages in descending
-  // order.
-  repeated Language detected_languages = 1;
-  // Adopted language code is the code of final determined language.
-  // It will be stored only if it's different from the first detected language.
-  optional string adopted_language_code = 2;
-}
-
-// User translated a page or interacted with translate suggestion.
-message Translation {
-  // Source language of the translation.
-  optional string from_language_code = 1;
-  // Target language of the translation.
-  optional string to_language_code = 2;
-  enum Interaction {
-    UNKNOWN = 0;
-    ACCEPT = 1;
-    DECLINE = 2;
-    // This happens when user scroll or click outside the UI without
-    // translation.
-    IGNORED = 3;
-    // This happens when user choose to close the translation window without
-    // translation.
-    DISMISSED = 4;
-    // User manually entered either language.
-    // In this case, from_language_code and to_language_code will be user chosen
-    // values.
-    MANUAL = 5;
-    // User choose to revert the translation, in this case, from_language_code
-    // and to_language_code will be previous chosen values.
-    TRANSLATION_REVERTED = 6;
-    // Automatically triggered translation.
-    // User sets always translate in user settings.
-    AUTO_TRANSLATION_BY_PREF = 7;
-    // User navigated through a click from a translated page.
-    AUTO_TRANSLATION_BY_LINK = 8;
-  }
-  optional Interaction interaction = 3;
-}
-
 message UserEventSpecifics {
   // Time of event, as measured by client in microseconds since Windows epoch.
   optional int64 event_time_usec = 1;
@@ -87,6 +29,67 @@ message UserEventSpecifics {
   // Used for testing and debugging EventLog system.
   message Test {}
 
+  // Reports field trial membership for the subset of trials that have been
+  // registered as important to other event types.
+  message FieldTrial {
+    message FieldTrialPair {
+      optional fixed32 name_id = 1;
+      optional fixed32 group_id = 2;
+    }
+    repeated FieldTrialPair field_trial_pairs = 1;
+  }
+
+  // Language detection output.
+  message LanguageDetection {
+    message Language {
+      // ISO 639 language code will be used.
+      optional string language_code = 1;
+      // Whether the detected language is reliable, note this is determined by
+      // the CLD3.
+      optional bool is_reliable = 2;
+    }
+    // Top n languages. Typically we just log the top language, but for page
+    // that we're not confident about, we may log up to 3 top languages in
+    // descending order.
+    repeated Language detected_languages = 1;
+    // Adopted language code is the code of final determined language.
+    // It will be stored only if it's different from the first detected
+    // language.
+    optional string adopted_language_code = 2;
+  }
+
+  // User translated a page or interacted with translate suggestion.
+  message Translation {
+    // Source language of the translation.
+    optional string from_language_code = 1;
+    // Target language of the translation.
+    optional string to_language_code = 2;
+    enum Interaction {
+      UNKNOWN = 0;
+      ACCEPT = 1;
+      DECLINE = 2;
+      // This happens when user scroll or click outside the UI without
+      // translation.
+      IGNORED = 3;
+      // This happens when user choose to close the translation window without
+      // translation.
+      DISMISSED = 4;
+      // User manually entered either language.
+      // In this case, from_language_code and to_language_code will be user
+      // chosen values.
+      MANUAL = 5;
+      // User choose to revert the translation, in this case, from_language_code
+      // and to_language_code will be previous chosen values.
+      TRANSLATION_REVERTED = 6;
+      // Automatically triggered translation.
+      // User sets always translate in user settings.
+      AUTO_TRANSLATION_BY_PREF = 7;
+      // User navigated through a click from a translated page.
+      AUTO_TRANSLATION_BY_LINK = 8;
+    }
+    optional Interaction interaction = 3;
+  }
+
   oneof event {
     Test test_event = 8;
     FieldTrial field_trial_event = 9;