Add UMA stats for pen palette

ash/common/system/chromeos/palette/palette_tool_manager.cc

Index: ash/common/system/chromeos/palette/palette_tool_manager.cc
diff --git a/ash/common/system/chromeos/palette/palette_tool_manager.cc b/ash/common/system/chromeos/palette/palette_tool_manager.cc
index f06900a16b276b98dab8da7be05dee965da99858..0161f31982026b1fb288fdabae5c7f92ddf23081 100644
--- a/ash/common/system/chromeos/palette/palette_tool_manager.cc
+++ b/ash/common/system/chromeos/palette/palette_tool_manager.cc
@@ -8,6 +8,7 @@
 
 #include "ash/common/system/chromeos/palette/palette_tool.h"
 #include "base/bind.h"
+#include "base/metrics/histogram_macros.h"
 #include "ui/gfx/vector_icons_public.h"
 
 namespace ash {
@@ -38,8 +39,20 @@ void PaletteToolManager::ActivateTool(PaletteToolId tool_id) {
   if (new_tool == previous_tool)
     return;
 
-  if (previous_tool)
+  if (previous_tool) {
     previous_tool->OnDisable();
+    if (previous_tool->GetToolId() == ash::PaletteToolId::LASER_POINTER) {

[jdufault, 2016/09/02 21:54:30]

nit: drop ash:: (already in the ash namespace)

[jdufault, 2016/09/02 21:54:30]

The only time we can cancel if is if we click the view again, right? What about
recording the cancel metrics inside of the "disable" if block of
CommonPaletteTool::OnViewClicked?

[xiaoyinh(OOO Sep 11-29), 2016/09/06 17:40:05]

Done.

[xiaoyinh(OOO Sep 11-29), 2016/09/06 17:40:05]

Done.

+      UMA_HISTOGRAM_ENUMERATION(
+          "Ash.Shelf.Palette.ModeCancellation",
+          ash::PaletteModeCancelType::PALETTE_MODE_LASER_POINTER_SWITCHED,
+          ash::PaletteModeCancelType::PALETTE_MODE_CANCEL_TYPE_COUNT);
+    } else if (previous_tool->GetToolId() == ash::PaletteToolId::MAGNIFY) {
+      UMA_HISTOGRAM_ENUMERATION(
+          "Ash.Shelf.Palette.ModeCancellation",
+          ash::PaletteModeCancelType::PALETTE_MODE_MAGNIFY_SWITCHED,
+          ash::PaletteModeCancelType::PALETTE_MODE_CANCEL_TYPE_COUNT);

[Ilya Sherman, 2016/09/02 21:39:30]

Please create a wrapper function for emitting to this histogram, that you could
call as

 
RecordPaletteModeCancellation(PaletteModeCancelType::PALETTE_MODE_MAGNIFY_SWITCHED)

(Note, by the way, that you're already in the "ash" namespace, and hence can
drop the "ash::" prefix.)

[xiaoyinh(OOO Sep 11-29), 2016/09/06 17:40:05]

Done.

+    }
+  }
 
   active_tools_[new_tool->GetGroup()] = new_tool;
   new_tool->OnEnable();
@@ -53,6 +66,17 @@ void PaletteToolManager::DeactivateTool(PaletteToolId tool_id) {
 
   active_tools_[tool->GetGroup()] = nullptr;
   tool->OnDisable();
+  if (tool->GetToolId() == ash::PaletteToolId::LASER_POINTER) {
+    UMA_HISTOGRAM_ENUMERATION(

[jdufault, 2016/09/02 21:54:30]

Should these UMA stats also have the AutoOpen check?

[xiaoyinh(OOO Sep 11-29), 2016/09/06 17:40:05]

AutoOpen factor are not specified for mode cancellation in the document.
So I didn't add it here. Let me know if you think it's necessary.

In general, clicks on view(including both mode activation and cancellation)
already considered autoOpened factor.  

+        "Ash.Shelf.Palette.ModeCancellation",
+        ash::PaletteModeCancelType::PALETTE_MODE_LASER_POINTER_CANCELLED,
+        ash::PaletteModeCancelType::PALETTE_MODE_CANCEL_TYPE_COUNT);
+  } else if (tool->GetToolId() == ash::PaletteToolId::MAGNIFY) {
+    UMA_HISTOGRAM_ENUMERATION(
+        "Ash.Shelf.Palette.ModeCancellation",
+        ash::PaletteModeCancelType::PALETTE_MODE_MAGNIFY_CANCELLED,
+        ash::PaletteModeCancelType::PALETTE_MODE_CANCEL_TYPE_COUNT);
+  }
 
   delegate_->OnActiveToolChanged();
 }
@@ -117,6 +141,10 @@ WmWindow* PaletteToolManager::GetWindow() {
   return delegate_->GetWindow();
 }
 
+void PaletteToolManager::RecordPaletteMetrics(ash::PaletteTrayOptions option) {
+  return delegate_->RecordPaletteMetrics(option);
+}
+
 PaletteTool* PaletteToolManager::FindToolById(PaletteToolId tool_id) {
   for (std::unique_ptr<PaletteTool>& tool : tools_) {
     if (tool->GetToolId() == tool_id)