Add UMA statistics to the clipboard

ui/base/clipboard/clipboard.cc

Index: ui/base/clipboard/clipboard.cc
diff --git a/ui/base/clipboard/clipboard.cc b/ui/base/clipboard/clipboard.cc
index e384c6528d70dbc4bdd01ad8832b5704d1f3864e..32cea0edd7e73c88cd2b2ca67245353b7ef6e77b 100644
--- a/ui/base/clipboard/clipboard.cc
+++ b/ui/base/clipboard/clipboard.cc
@@ -9,6 +9,7 @@
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/metrics/histogram.h"
 #include "base/synchronization/lock.h"
 #include "ui/gfx/size.h"
 
@@ -103,6 +104,8 @@ union SourceTag2BinaryHelper {
 
 }  // namespace
 
+const Clipboard::SourceTag Clipboard::kInvalidSourceTag =
+    reinterpret_cast<void*>(1);
 const char Clipboard::kMimeTypeText[] = "text/plain";
 const char Clipboard::kMimeTypeURIList[] = "text/uri-list";
 const char Clipboard::kMimeTypeDownloadURL[] = "downloadurl";
@@ -186,6 +189,8 @@ void Clipboard::WriteObjects(Buffer buffer,
   WriteObjectsImpl(buffer, objects, tag);
   if (!write_objects_callback_.is_null())
     write_objects_callback_.Run(buffer);
+  ReportAction(buffer, tag == SourceTag() ? WRITE_CLIPBOARD_NO_SOURCE_TAG
+                                          : WRITE_CLIPBOARD_SOURCE_TAG);
 }
 
 void Clipboard::DispatchObject(ObjectType type, const ObjectMapParams& params) {
@@ -299,4 +304,31 @@ void Clipboard::ReplaceSharedMemHandle(ObjectMap* objects,
   }
 }
 
+void Clipboard::ReportAction(Buffer buffer, TrackedAction action) const
+{
+  if (buffer != BUFFER_STANDARD)
+    return;
+
+  switch (action) {
+    case WRITE_CLIPBOARD_NO_SOURCE_TAG:
+    case WRITE_CLIPBOARD_SOURCE_TAG:
+      UMA_HISTOGRAM_ENUMERATION("Clipboard.IncognitoUseCase",
+                                action,
+                                MAX_TRACKED_ACTION);
+      break;
+    // The code below counts cases when there is the kInvalidSourceTag in the
+    // clipboard. That is, original data came from Incognito window and was
+    // destroyed with that window.
+    case READ_TEXT:
+      if (kInvalidSourceTag == ReadSourceTag(buffer)) {
+        UMA_HISTOGRAM_ENUMERATION("Clipboard.IncognitoUseCase",
+                                  action,
+                                  MAX_TRACKED_ACTION);
+      }
+      break;
+    case MAX_TRACKED_ACTION:
+      break;
+  }
+}
+
 }  // namespace ui