Add IdleTask API to v8::Platform.

include/v8-platform.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_V8_PLATFORM_H_
 #define V8_V8_PLATFORM_H_
 
 namespace v8 {
 
 class Isolate;
 
 /**
  * A Task represents a unit of work.
  */
 class Task {
  public:
   virtual ~Task() {}
 
   virtual void Run() = 0;
 };
 
+
+/**
+* An IdleTask represents a unit of work to be performed in idle time.
+* The Run method is invoked with an argument that specifies the deadline in
+* seconds returned by MonotonicallyIncreasingTime().
+* The idle task is expected to complete by this deadline.
+*/
+class IdleTask {
+ public:
+  virtual ~IdleTask() {}
+  virtual void Run(double deadline_in_seconds) = 0;
+};
+
+
 /**
  * V8 Platform abstraction layer.
  *
  * The embedder has to provide an implementation of this interface before
  * initializing the rest of V8.
  */
 class Platform {
  public:
   /**
    * This enum is used to indicate whether a task is potentially long running,
@@ skipping 24 matching lines @@
    */
   virtual void CallOnForegroundThread(Isolate* isolate, Task* task) = 0;
 
   /**
    * Schedules a task to be invoked on a foreground thread wrt a specific
    * |isolate| after the given number of seconds |delay_in_seconds|.
    * Tasks posted for the same isolate should be execute in order of
    * scheduling. The definition of "foreground" is opaque to V8.
    */
   virtual void CallDelayedOnForegroundThread(Isolate* isolate, Task* task,
-                                             double delay_in_seconds) {
+                                             double delay_in_seconds) = 0;
+
+  /**
+   * Schedules a task to be invoked on a foreground thread wrt a specific
+   * |isolate| when the embedder is idle.
+   * Requires that SupportsIdleTasks(isolate) is true.
+   * Idle tasks may be reordered relative to other task types and may be
+   * starved for an arbitrarily long time if no idle time is available.
+   * The definition of "foreground" is opaque to V8.
+   */
+  virtual void CallIdleOnForegroundThread(Isolate* isolate, IdleTask* task) {
     // TODO(ulan): Make this function abstract after V8 roll in Chromium.
   }
 
   /**
+   * Returns true if idle tasks are enabled for the given |isolate|.
+   */
+  virtual bool IdleTasksEnabled(Isolate* isolate) {
+    // TODO(ulan): Make this function abstract after V8 roll in Chromium.
+    return false;
+  }
+
+  /**
    * Monotonically increasing time in seconds from an arbitrary fixed point in
    * the past. This function is expected to return at least
    * millisecond-precision values. For this reason,
    * it is recommended that the fixed point be no further in the past than
    * the epoch.
    **/
   virtual double MonotonicallyIncreasingTime() = 0;
 };
 
 }  // namespace v8
 
 #endif  // V8_V8_PLATFORM_H_