Add step OverAwait to service protocol

runtime/vm/service/service.md

 # Dart VM Service Protocol 3.2
 
 > Please post feedback to the [observatory-discuss group][discuss-list]
 
 This document describes of _version 3.2_ of the Dart VM Service Protocol. This
 protocol is used to communicate with a running Dart Virtual Machine.
 
 To use the Service Protocol, start the VM with the *--observe* flag.
 The VM will start a webserver which services protocol requests via WebSocket.
 It is possible to make HTTP (non-WebSocket) requests,
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 ### Breakpoint
 
 ```
 class Breakpoint extends Object {
   // A number identifying this breakpoint to the user.
   int breakpointNumber;
 
   // Has this breakpoint been assigned to a specific program location?
   bool resolved;
 
+  // Is this a breakpoint that was added synthetically as part of a step
+  // OverAsyncSuspension resume command?
+  bool isSyntheticAsyncContinuation [optional].
+
   // SourceLocation when breakpoint is resolved, UnresolvedSourceLocation
   // when a breakpoint is not resolved.
   SourceLocation|UnresolvedSourceLocation location;
 }
 ```
 
 A _Breakpoint_ describes a debugger breakpoint.
 
 A breakpoint is _resolved_ when it has been assigned to a specific
 program location.  A breakpoint my remain unresolved when it is in
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   // The extension event kind.
   //
   // This is provided for the Extension event.
   string extensionKind [optional];
 
   // The extension event data.
   //
   // This is provided for the Extension event.
   ExtensionData extensionData [optional];
+
+  // Is the isolate paused at an await, yield, or yield* statement?
+  //
+  // This is provided for the event kinds:
+  //   PauseBreakpoint
+  //   PauseInterrupted
+  bool atAsyncSuspension [optional]
 }
 ```
 
 An _Event_ is an asynchronous notification from the VM. It is delivered
 only when the client has subscribed to an event stream using the
 [streamListen](#streamListen) RPC.
 
 For more information, see [events](#events).
 
 ### EventKind
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 An _ExceptionPauseMode_ indicates how the isolate pauses when an exception
 is thrown.
 
 ### StepOption
 
 ```
 enum StepOption {
   Into,
   Over,
+  OverAsyncSuspension,
   Out
 }
 ```
 
 A _StepOption_ indicates which form of stepping is requested in a [resume](#resume) RPC.
 
 ### Success
 
 ```
 class Success extends Response {
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 ## Revision History
 
 version | comments
 ------- | --------
 1.0 | initial revision
 2.0 | Describe protocol version 2.0.
 3.0 | Describe protocol version 3.0.  Added UnresolvedSourceLocation.  Added Sentinel return to getIsolate.  Add AddedBreakpointWithScriptUri.  Removed Isolate.entry. The type of VM.pid was changed from string to int.  Added VMUpdate events.  Add offset and count parameters to getObject() and offset and count fields to Instance. Added ServiceExtensionAdded event.
 3.1 | Add the getSourceReport RPC.  The getObject RPC now accepts offset and count for string objects.  String objects now contain length, offset, and count properties.
 3.2 | Isolate objects now include the runnable bit and many debugger related RPCs will return an error if executed on an isolate before it is runnable.
-
+3.3 | Pause event now indicates if the isolate is paused at an await, yield, or yield* suspension point via the 'atAsyncSuspension' field. Resume command now supports the step parameter 'OverAsyncSuspension'. A Breakpoint added synthetically by an 'OverAsyncSuspension' resume command identifies itself as such via the 'isSyntheticAsyncContinuation' field.
 
 [discuss-list]: https://groups.google.com/a/dartlang.org/forum/#!forum/observatory-discuss