Add a UMA histogram to count accessibility usage.

Deletes code that incorrectly used a stat counter instead of a histogram,
and adds a function that runs 10 seconds after the browser starts and
updates a UMA enum histogram with the status of whether accessibility is
enabled or not. Also makes it so that manually enabling accessibility
from the command-line triggers this as well - we may want to separate
this out later.

BUG=99504
TEST=none
Review URL: http://codereview.chromium.org/8479015

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@108797 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 43 insertions, 9 deletions

diff --git a/content/browser/accessibility/browser_accessibility_state.cc b/content/browser/accessibility/browser_accessibility_state.cc
index 45b3a3b..bb277b7 100644
--- a/content/browser/accessibility/browser_accessibility_state.cc
+++ b/content/browser/accessibility/browser_accessibility_state.cc
@@ -5,9 +5,19 @@
 #include "content/browser/accessibility/browser_accessibility_state.h"
 
 #include "base/memory/singleton.h"
+#include "base/metrics/histogram.h"
+#include "base/timer.h"
+
+// Update the accessibility histogram 45 seconds after initialization.
+static const int kAccessibilityHistogramDelaySecs = 45;
 
 BrowserAccessibilityState::BrowserAccessibilityState()
-    : screen_reader_active_(false) {
+    : accessibility_enabled_(false) {
+  update_histogram_timer_.Start(
+      FROM_HERE,
+      base::TimeDelta::FromSeconds(kAccessibilityHistogramDelaySecs),
+      this,
+      &BrowserAccessibilityState::UpdateHistogram);
 }
 
 BrowserAccessibilityState::~BrowserAccessibilityState() {
@@ -19,9 +29,20 @@ BrowserAccessibilityState* BrowserAccessibilityState::GetInstance() {
 }
 
 void BrowserAccessibilityState::OnScreenReaderDetected() {
-  screen_reader_active_ = true;
+  accessibility_enabled_ = true;
+}
+
+void BrowserAccessibilityState::OnAccessibilityEnabledManually() {
+  // We may want to do something different with this later.
+  accessibility_enabled_ = true;
 }
 
 bool BrowserAccessibilityState::IsAccessibleBrowser() {
-  return screen_reader_active_;
+  return accessibility_enabled_;
+}
+
+void BrowserAccessibilityState::UpdateHistogram() {
+  UMA_HISTOGRAM_ENUMERATION("Accessibility.State",
+                            accessibility_enabled_ ? 1 : 0,
+                            2);
 }
diff --git a/content/browser/accessibility/browser_accessibility_state.h b/content/browser/accessibility/browser_accessibility_state.h
index 62e19eb..c0e2048 100644
--- a/content/browser/accessibility/browser_accessibility_state.h
+++ b/content/browser/accessibility/browser_accessibility_state.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include "base/basictypes.h"
+#include "base/timer.h"
 #include "content/common/content_export.h"
 
 template <typename T> struct DefaultSingletonTraits;
@@ -35,18 +36,28 @@ class CONTENT_EXPORT BrowserAccessibilityState {
 
   ~BrowserAccessibilityState();
 
+  // Called when accessibility is enabled manually (via command-line flag).
+  void OnAccessibilityEnabledManually();
+
   // Called when screen reader client is detected.
   void OnScreenReaderDetected();
 
   // Returns true if the browser should be customized for accessibility.
   bool IsAccessibleBrowser();
 
+  // Called a short while after startup to allow time for the accessibility
+  // state to be determined. Updates a histogram with the current state.
+  void UpdateHistogram();
+
  private:
   BrowserAccessibilityState();
   friend struct DefaultSingletonTraits<BrowserAccessibilityState>;
 
-  // Set to true when a screen reader client is detected.
-  bool screen_reader_active_;
+  // Set to true when full accessibility features should be enabled.
+  bool accessibility_enabled_;
+
+  // Timer to update the histogram a short while after startup.
+  base::OneShotTimer<BrowserAccessibilityState> update_histogram_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserAccessibilityState);
 };
diff --git a/content/browser/renderer_host/render_widget_host.cc b/content/browser/renderer_host/render_widget_host.cc
index 4a64feb..bb1d5ba 100644
--- a/content/browser/renderer_host/render_widget_host.cc
+++ b/content/browser/renderer_host/render_widget_host.cc
@@ -10,7 +10,6 @@
 #include "base/i18n/rtl.h"
 #include "base/message_loop.h"
 #include "base/metrics/histogram.h"
-#include "base/metrics/stats_counters.h"
 #include "base/utf_string_conversions.h"
 #include "content/browser/accessibility/browser_accessibility_state.h"
 #include "content/browser/gpu/gpu_process_host.h"
@@ -110,9 +109,13 @@ RenderWidgetHost::RenderWidgetHost(RenderProcessHost* process,
   // tell the process host that we're alive.
   process_->WidgetRestored();
 
+  // Enable accessibility if it was manually specified or if it was
+  // auto-detected.
   if (CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kForceRendererAccessibility) ||
-      BrowserAccessibilityState::GetInstance()->IsAccessibleBrowser()) {
+          switches::kForceRendererAccessibility)) {
+    BrowserAccessibilityState::GetInstance()->OnAccessibilityEnabledManually();
+    EnableRendererAccessibility();
+  } else if (BrowserAccessibilityState::GetInstance()->IsAccessibleBrowser()) {
     EnableRendererAccessibility();
   }
 }
@@ -1267,7 +1270,6 @@ void RenderWidgetHost::EnableRendererAccessibility() {
     return;
   }
 
-  SIMPLE_STATS_COUNTER("Accessibility.SessionCount");
   renderer_accessible_ = true;
 
   if (process_->HasConnection()) {