Doxygenize the documentation comments

There were many // comment used to document classes, functions etc. but
those are not picked up by doxygen which expects /// comments. This
converts many comments from // to /// in order to improve the generated
documentation.

BUG=
R=jvoung@chromium.org, kschimpf@google.com

Review URL: https://codereview.chromium.org/1216963007.
diff --git a/src/IceTimerTree.h b/src/IceTimerTree.h
index dd8dcf1..aabeb29 100644
--- a/src/IceTimerTree.h
+++ b/src/IceTimerTree.h
@@ -6,10 +6,11 @@
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
-//
-// This file declares the TimerTree class, which allows flat and
-// cumulative execution time collection of call chains.
-//
+///
+/// \file
+/// This file declares the TimerTree class, which allows flat and
+/// cumulative execution time collection of call chains.
+///
 //===----------------------------------------------------------------------===//
 
 #ifndef SUBZERO_SRC_ICETIMERTREE_H
@@ -25,23 +26,23 @@
   TimerStack() = delete;
   TimerStack &operator=(const TimerStack &) = delete;
 
-  // Timer tree index type.  A variable of this type is used to access
-  // an interior, not-necessarily-leaf node of the tree.
+  /// Timer tree index type.  A variable of this type is used to access
+  /// an interior, not-necessarily-leaf node of the tree.
   typedef std::vector<class TimerTreeNode>::size_type TTindex;
-  // Representation of a path of leaf values leading to a particular
-  // node.  The representation happens to be in "reverse" order,
-  // i.e. from leaf/interior to root, for implementation efficiency.
+  /// Representation of a path of leaf values leading to a particular
+  /// node.  The representation happens to be in "reverse" order,
+  /// i.e. from leaf/interior to root, for implementation efficiency.
   typedef llvm::SmallVector<TTindex, 8> PathType;
-  // Representation of a mapping of leaf node indexes from one timer
-  // stack to another.
+  /// Representation of a mapping of leaf node indexes from one timer
+  /// stack to another.
   typedef std::vector<TimerIdT> TranslationType;
 
-  // TimerTreeNode represents an interior or leaf node in the call tree.
-  // It contains a list of children, a pointer to its parent, and the
-  // timer ID for the node.  It also holds the cumulative time spent at
-  // this node and below.  The children are always at a higher index in
-  // the TimerTreeNode::Nodes array, and the parent is always at a lower
-  // index.
+  /// TimerTreeNode represents an interior or leaf node in the call tree.
+  /// It contains a list of children, a pointer to its parent, and the
+  /// timer ID for the node.  It also holds the cumulative time spent at
+  /// this node and below.  The children are always at a higher index in
+  /// the TimerTreeNode::Nodes array, and the parent is always at a lower
+  /// index.
   class TimerTreeNode {
     TimerTreeNode &operator=(const TimerTreeNode &) = delete;
 
@@ -84,12 +85,12 @@
   double FirstTimestamp;
   double LastTimestamp;
   uint64_t StateChangeCount = 0;
-  // IDsIndex maps a symbolic timer name to its integer ID.
+  /// IDsIndex maps a symbolic timer name to its integer ID.
   std::map<IceString, TimerIdT> IDsIndex;
-  std::vector<IceString> IDs;       // indexed by TimerIdT
-  std::vector<TimerTreeNode> Nodes; // indexed by TTindex
-  std::vector<double> LeafTimes;    // indexed by TimerIdT
-  std::vector<size_t> LeafCounts;   // indexed by TimerIdT
+  std::vector<IceString> IDs;       /// indexed by TimerIdT
+  std::vector<TimerTreeNode> Nodes; /// indexed by TTindex
+  std::vector<double> LeafTimes;    /// indexed by TimerIdT
+  std::vector<size_t> LeafCounts;   /// indexed by TimerIdT
   TTindex StackTop = 0;
 };