Bug 1197145 - Added BaseTimeDuration::IsZero(), BaseTimeDuration::operator bool(), TimeStamp::operator bool(). r=nfroyd

mozglue/misc/TimeStamp.h

@@ -258,6 +258,14 @@ public:
   {
     return mValue != aOther.mValue;
   }
+  bool IsZero() const
+  {
+    return mValue == 0;
+  }
+  explicit operator bool() const
+  {
+    return mValue != 0;
+  }
 
   // Return a best guess at the system's current timing resolution,
   // which might be variable.  BaseTimeDurations below this order of
@@ -413,6 +421,15 @@ public:
    */
   bool IsNull() const { return mValue == 0; }
 
+  /**
+   * Return true if this is not the "null" moment, may be used in tests, e.g.:
+   * |if (timestamp) { ... }|
+   */
+  explicit operator bool() const
+  {
+    return mValue != 0;
+  }
+
   /**
    * Return a timestamp reflecting the current elapsed system time. This
    * is monotonically increasing (i.e., does not decrease) over the