Add support for faster, more limited accessibility modes.

content/browser/accessibility/browser_accessibility_state_impl.cc

Index: content/browser/accessibility/browser_accessibility_state_impl.cc
diff --git a/content/browser/accessibility/browser_accessibility_state_impl.cc b/content/browser/accessibility/browser_accessibility_state_impl.cc
index 4c50bb32dd2fa96194868c70b952b22f6f582039..ff2e5d19bdca2e77a0e0a3be0b608242f623e1a1 100644
--- a/content/browser/accessibility/browser_accessibility_state_impl.cc
+++ b/content/browser/accessibility/browser_accessibility_state_impl.cc
@@ -17,6 +17,21 @@
 
 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;
 
@@ -133,7 +148,38 @@ void BrowserAccessibilityStateImpl::AddAccessibilityModeFlags(
     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)