[BackgroundTaskScheduler] Update proto

The option to schedule tasks at exact times will be added to the
BackgroundTaskScheduler. Because these types of tasks will be scheduled
with AlarmManager, additional information needs to be added to the
BackgroundTaskScheduler storage.

This CL makes the necessary changes to the Protocol Buffer that stores a
scheduled task.

Bug: 970160
Change-Id: Ica396c0fa3ec27b1ffe50f99d56e0f5c83ac38fd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1765850Reviewed-by: Tommy Nyquist <nyquist@chromium.org>
Reviewed-by: Mugdha Lakhani <nator@chromium.org>
Commit-Queue: Ioana Stefan <ioanastefan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691778}

components/background_task_scheduler/android/java/src/org/chromium/components/background_task_scheduler/scheduled_task.proto

@@ -11,4 +11,47 @@ package background_task_scheduler;
 option java_package = "org.chromium.components.background_task_scheduler";
 option java_outer_classname = "ScheduledTaskProto";
 
-message ScheduledTask {}
\ No newline at end of file
+message ScheduledTask {
+  enum Type {
+    ONE_OFF = 0;
+    PERIODIC = 1;
+    EXACT = 2;
+  }
+
+  // The type of the scheduled task.
+  Type type = 1;
+
+  // UTC timestamp at which an ExactTask will be triggered by AlarmManager.
+  int64 trigger_ms = 2;
+
+  message ExtraItem {
+    enum Type {
+      BOOLEAN = 0;
+      BOOLEAN_ARRAY = 1;
+      DOUBLE = 2;
+      DOUBLE_ARRAY = 3;
+      INT = 4;
+      INT_ARRAY = 5;
+      LONG = 6;
+      LONG_ARRAY = 7;
+      STRING = 8;
+      STRING_ARRAY = 9;
+    }
+
+    // The key set for this item in the extras.
+    string key = 1;
+
+    // The type of the value associated with this item.
+    Type type = 2;
+
+    // Serialized form of the value set for this item in the extras.
+    // Non-array types will store only one element in this repeated field.
+    // All the types supported in the extras field are serializable.
+    repeated string values = 3;
+  }
+
+  // Extras for the BackgroundTask, stored for an ExactTask. OneOffTask and
+  // PeriodicTask objects store their extras through their scheduling backend
+  // (JobScheduler and GcmNetworkManager).
+  repeated ExtraItem extras = 3;
+}
\ No newline at end of file