Add support for faster, more limited accessibility modes.

content/browser/accessibility/browser_accessibility_state_impl.cc

 // Copyright (c) 2012 The Chromium 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 "content/browser/accessibility/browser_accessibility_state_impl.h"
 
 #include <stddef.h>
 
 #include "base/command_line.h"
 #include "base/metrics/histogram_macros.h"
 #include "build/build_config.h"
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 #include "content/browser/web_contents/web_contents_impl.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/common/content_switches.h"
 #include "ui/gfx/color_utils.h"
 
 namespace content {
 
+// IMPORTANT!
+// These values are written to logs.  Do not renumber or delete
+// existing items; add new entries to the end of the list.
+enum {
+  UMA_AX_MODE_FLAG_NATIVE_APIS = 0,
+  UMA_AX_MODE_FLAG_WEB_CONTENTS = 1,
+  UMA_AX_MODE_FLAG_INLINE_TEXT_BOXES = 2,
+  UMA_AX_MODE_FLAG_SCREEN_READER = 3,
+  UMA_AX_MODE_FLAG_HTML = 4,
+
+  // This must always be the last enum. It's okay for its value to
+  // increase, but none of the other enum values may change.
+  UMA_AX_MODE_FLAG_MAX
+};
+
 // Update the accessibility histogram 45 seconds after initialization.
 static const int kAccessibilityHistogramDelaySecs = 45;
 
 // static
 BrowserAccessibilityState* BrowserAccessibilityState::GetInstance() {
   return BrowserAccessibilityStateImpl::GetInstance();
 }
 
 // static
 BrowserAccessibilityStateImpl* BrowserAccessibilityStateImpl::GetInstance() {
@@ skipping 96 matching lines @@
 }
 #endif
 
 void BrowserAccessibilityStateImpl::AddAccessibilityModeFlags(
     AccessibilityMode mode) {
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kDisableRendererAccessibility)) {
     return;
   }
 
+  AccessibilityMode previous_mode = accessibility_mode_;
   accessibility_mode_ |= mode;
+  if (accessibility_mode_ == previous_mode)
+    return;
+
+  AccessibilityMode new_mode_flags = accessibility_mode_ & (~previous_mode);
+  if (new_mode_flags & ACCESSIBILITY_MODE_FLAG_NATIVE_APIS) {
+    UMA_HISTOGRAM_ENUMERATION("Accessibility.ModeFlag",
+                              UMA_AX_MODE_FLAG_NATIVE_APIS,
+                              UMA_AX_MODE_FLAG_MAX);

[Ilya Sherman, 2016/12/17 00:57:12]

nit: Please factor out a function for recording to this histogram, invoked as
"RecordAccessibilityModeFlag(UMA_AX_MODE_FLAG_NATIVE_APIS)".

[dmazzoni, 2016/12/19 22:51:50]

Done.

+  }
+  if (new_mode_flags & ACCESSIBILITY_MODE_FLAG_WEB_CONTENTS) {
+    UMA_HISTOGRAM_ENUMERATION("Accessibility.ModeFlag",
+                              UMA_AX_MODE_FLAG_WEB_CONTENTS,
+                              UMA_AX_MODE_FLAG_MAX);
+  }
+  if (new_mode_flags & ACCESSIBILITY_MODE_FLAG_INLINE_TEXT_BOXES) {
+    UMA_HISTOGRAM_ENUMERATION("Accessibility.ModeFlag",
+                              UMA_AX_MODE_FLAG_INLINE_TEXT_BOXES,
+                              UMA_AX_MODE_FLAG_MAX);
+  }
+  if (new_mode_flags & ACCESSIBILITY_MODE_FLAG_SCREEN_READER) {
+    UMA_HISTOGRAM_ENUMERATION("Accessibility.ModeFlag",
+                              UMA_AX_MODE_FLAG_SCREEN_READER,
+                              UMA_AX_MODE_FLAG_MAX);
+  }
+  if (new_mode_flags & ACCESSIBILITY_MODE_FLAG_HTML) {
+    UMA_HISTOGRAM_ENUMERATION("Accessibility.ModeFlag",
+                              UMA_AX_MODE_FLAG_HTML,
+                              UMA_AX_MODE_FLAG_MAX);
+  }
+
   std::vector<WebContentsImpl*> web_contents_vector =
       WebContentsImpl::GetAllWebContents();
   for (size_t i = 0; i < web_contents_vector.size(); ++i)
     web_contents_vector[i]->AddAccessibilityMode(accessibility_mode_);
 }
 
 void BrowserAccessibilityStateImpl::RemoveAccessibilityModeFlags(
     AccessibilityMode mode) {
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kForceRendererAccessibility) &&
       mode == ACCESSIBILITY_MODE_COMPLETE) {
     return;
   }
 
   accessibility_mode_ = accessibility_mode_ ^ (mode & accessibility_mode_);
   std::vector<WebContentsImpl*> web_contents_vector =
       WebContentsImpl::GetAllWebContents();
   for (size_t i = 0; i < web_contents_vector.size(); ++i)
     web_contents_vector[i]->SetAccessibilityMode(accessibility_mode());
 }
 
 }  // namespace content