[debugger] track debugger feature usage via histogram.

src/debug/debug.cc

 // Copyright 2012 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.
 
 #include "src/debug/debug.h"
 
 #include "src/api.h"
 #include "src/arguments.h"
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 25 matching lines @@
       command_queue_(isolate->logger(), kQueueInitialSize),
       is_active_(false),
       is_suppressed_(false),
       live_edit_enabled_(true),  // TODO(yangguo): set to false by default.
       break_disabled_(false),
       break_points_active_(true),
       in_debug_event_listener_(false),
       break_on_exception_(false),
       break_on_uncaught_exception_(false),
       debug_info_list_(NULL),
+      feature_tracker_(isolate),
       isolate_(isolate) {
   ThreadInit();
 }
 
 
 static v8::Local<v8::Context> GetDebugEventContext(Isolate* isolate) {
   Handle<Context> context = isolate->debug()->debugger_entry()->GetContext();
   // Isolate::context() may have been NULL when "script collected" event
   // occured.
   if (context.is_null()) return v8::Local<v8::Context>();
@@ skipping 253 matching lines @@
   }
   return false;
 }
 
 
 Handle<Object> BreakLocation::BreakPointObjects() const {
   return debug_info_->GetBreakPointObjects(pc_offset_);
 }
 
 
+void DebugFeatureTracker::Track(DebugFeatureTracker::Feature feature) {
+  uint32_t mask = 1 << feature;
+  // Only count one sample per feature and isolate.
+  if (bitfield_ & mask) return;
+  isolate_->counters()->debug_feature_usage()->AddSample(feature);
+  bitfield_ |= mask;
+}
+
+
 // Threading support.
 void Debug::ThreadInit() {
   thread_local_.break_count_ = 0;
   thread_local_.break_id_ = 0;
   thread_local_.break_frame_id_ = StackFrame::NO_ID;
   thread_local_.last_step_action_ = StepNone;
   thread_local_.last_statement_position_ = RelocInfo::kNoPosition;
   thread_local_.step_count_ = 0;
   thread_local_.last_fp_ = 0;
   thread_local_.queued_step_count_ = 0;
@@ skipping 60 matching lines @@
   ExtensionConfiguration no_extensions;
   Handle<Context> context = isolate_->bootstrapper()->CreateEnvironment(
       MaybeHandle<JSGlobalProxy>(), v8::Local<ObjectTemplate>(), &no_extensions,
       DEBUG_CONTEXT);
 
   // Fail if no context could be created.
   if (context.is_null()) return false;
 
   debug_context_ = Handle<Context>::cast(
       isolate_->global_handles()->Create(*context));
+
+  feature_tracker()->Track(DebugFeatureTracker::kActive);
+
   return true;
 }
 
 
 void Debug::Unload() {
   ClearAllBreakPoints();
   ClearStepping();
 
   // Return debugger is not loaded.
   if (!is_loaded()) return;
@@ skipping 209 matching lines @@
   Handle<DebugInfo> debug_info(shared->GetDebugInfo());
   // Source positions starts with zero.
   DCHECK(*source_position >= 0);
 
   // Find the break point and change it.
   BreakLocation location = BreakLocation::FromPosition(
       debug_info, ALL_BREAK_LOCATIONS, *source_position, STATEMENT_ALIGNED);
   *source_position = location.statement_position();
   location.SetBreakPoint(break_point_object);
 
+  feature_tracker()->Track(DebugFeatureTracker::kBreakPoint);
+
   // At least one active break point now.
   return debug_info->GetBreakPointCount() > 0;
 }
 
 
 bool Debug::SetBreakPointForScript(Handle<Script> script,
                                    Handle<Object> break_point_object,
                                    int* source_position,
                                    BreakPositionAlignment alignment) {
   HandleScope scope(isolate_);
@@ skipping 21 matching lines @@
 
   Handle<DebugInfo> debug_info(shared->GetDebugInfo());
   // Source positions starts with zero.
   DCHECK(position >= 0);
 
   // Find the break point and change it.
   BreakLocation location = BreakLocation::FromPosition(
       debug_info, ALL_BREAK_LOCATIONS, position, alignment);
   location.SetBreakPoint(break_point_object);
 
+  feature_tracker()->Track(DebugFeatureTracker::kBreakPoint);
+
   position = (alignment == STATEMENT_ALIGNED) ? location.statement_position()
                                               : location.position();
 
   *source_position = position + shared->start_position();
 
   // At least one active break point now.
   DCHECK(debug_info->GetBreakPointCount() > 0);
   return true;
 }
 
@@ skipping 188 matching lines @@
   if (id == StackFrame::NO_ID) {
     // If there is no JavaScript stack don't do anything.
     return;
   }
   if (frame_id != StackFrame::NO_ID) {
     id = frame_id;
   }
   JavaScriptFrameIterator frames_it(isolate_, id);
   JavaScriptFrame* frame = frames_it.frame();
 
+  feature_tracker()->Track(DebugFeatureTracker::kStepping);
+
   // First of all ensure there is one-shot break points in the top handler
   // if any.
   FloodHandlerWithOneShot();
 
   // If the function on the top frame is unresolved perform step out. This will
   // be the case when calling unknown function and having the debugger stopped
   // in an unhandled exception.
   if (!frame->function()->IsJSFunction()) {
     // Step out: Find the calling JavaScript frame and flood it with
     // breakpoints.
@@ skipping 1715 matching lines @@
 }
 
 
 void LockingCommandMessageQueue::Clear() {
   base::LockGuard<base::Mutex> lock_guard(&mutex_);
   queue_.Clear();
 }
 
 }  // namespace internal
 }  // namespace v8