Collect UMA statistics on which chrome://flags lead to chrome restart on ChromeOS.

chrome/browser/about_flags.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 "chrome/browser/about_flags.h"
 
 #include <iterator>
 #include <map>
 #include <set>
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/memory/singleton.h"
+#include "base/metrics/sparse_histogram.h"
+#include "base/numerics/safe_conversions.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
 #include "cc/base/switches.h"
 #include "chrome/browser/bookmarks/enhanced_bookmarks_features.h"
 #include "chrome/browser/flags_storage.h"
 #include "chrome/common/chrome_content_client.h"
 #include "chrome/common/chrome_switches.h"
 #include "components/autofill/core/common/autofill_switches.h"
 #include "components/cloud_devices/common/cloud_devices_switches.h"
+#include "components/metrics/metrics_hashes.h"
 #include "components/nacl/common/nacl_switches.h"
 #include "components/search/search_switches.h"
 #include "content/public/browser/user_metrics.h"
 #include "extensions/common/switches.h"
 #include "grit/chromium_strings.h"
 #include "grit/generated_resources.h"
 #include "grit/google_chrome_strings.h"
 #include "media/base/media_switches.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/ui_base_switches.h"
@@ skipping 21 matching lines @@
 #endif
 
 #if defined(ENABLE_APP_LIST)
 #include "ui/app_list/app_list_switches.h"
 #endif
 
 using base::UserMetricsAction;
 
 namespace about_flags {
 
+const uint32_t kBadSwitchFormatHistogramId = 0;
+
 // Macros to simplify specifying the type.
 #define SINGLE_VALUE_TYPE_AND_VALUE(command_line_switch, switch_value) \
     Experiment::SINGLE_VALUE, \
     command_line_switch, switch_value, NULL, NULL, NULL, 0
 #define SINGLE_VALUE_TYPE(command_line_switch) \
     SINGLE_VALUE_TYPE_AND_VALUE(command_line_switch, "")
 #define ENABLE_DISABLE_VALUE_TYPE_AND_VALUE(enable_switch, enable_value, \
                                             disable_switch, disable_value) \
     Experiment::ENABLE_DISABLE_VALUE, enable_switch, enable_value, \
     disable_switch, disable_value, NULL, 3
@@ skipping 449 matching lines @@
 // To add a new experiment add to the end of kExperiments. There are two
 // distinct types of experiments:
 // . SINGLE_VALUE: experiment is either on or off. Use the SINGLE_VALUE_TYPE
 //   macro for this type supplying the command line to the macro.
 // . MULTI_VALUE: a list of choices, the first of which should correspond to a
 //   deactivated state for this lab (i.e. no command line option).  To specify
 //   this type of experiment use the macro MULTI_VALUE_TYPE supplying it the
 //   array of choices.
 // See the documentation of Experiment for details on the fields.
 //
+// Command-line switches must have entries in enum "LoginCustomFlags" in
+// histograms.xml. See note in histograms.xml and don't forget to run
+// AboutFlagsHistogramTest unit test to calculate and verify checksum.
+//
 // When adding a new choice, add it to the end of the list.
 const Experiment kExperiments[] = {
   {
     "ignore-gpu-blacklist",
     IDS_FLAGS_IGNORE_GPU_BLACKLIST_NAME,
     IDS_FLAGS_IGNORE_GPU_BLACKLIST_DESCRIPTION,
     kOsAll,
     SINGLE_VALUE_TYPE(switches::kIgnoreGpuBlacklist)
   },
   {
@@ skipping 1377 matching lines @@
     kOsAll,
     MULTI_VALUE_TYPE(kEnableDropSyncCredentialChoices)
   },
   {
     "enable-extension-action-redesign",
     IDS_FLAGS_ENABLE_EXTENSION_ACTION_REDESIGN_NAME,
     IDS_FLAGS_ENABLE_EXTENSION_ACTION_REDESIGN_DESCRIPTION,
     kOsWin | kOsLinux | kOsCrOS,
     SINGLE_VALUE_TYPE(extensions::switches::kEnableExtensionActionRedesign)
   },
+  // NOTE: Adding new command-line switches requires adding corresponding
+  // entries to enum "LoginCustomFlags" in histograms.xml. See note in
+  // histograms.xml and don't forget to run AboutFlagsHistogramTest unit test.
 };
 
 const Experiment* experiments = kExperiments;
 size_t num_experiments = arraysize(kExperiments);
 
 // Stores and encapsulates the little state that about:flags has.
 class FlagsState {
  public:
   FlagsState() : needs_restart_(false) {}
   void ConvertFlagsToSwitches(FlagsStorage* flags_storage,
@@ skipping 191 matching lines @@
 
 void ConvertFlagsToSwitches(FlagsStorage* flags_storage,
                             CommandLine* command_line,
                             SentinelsMode sentinels) {
   FlagsState::GetInstance()->ConvertFlagsToSwitches(flags_storage,
                                                     command_line,
                                                     sentinels);
 }
 
 bool AreSwitchesIdenticalToCurrentCommandLine(
-    const CommandLine& new_cmdline, const CommandLine& active_cmdline) {
+    const CommandLine& new_cmdline,
+    const CommandLine& active_cmdline,
+    std::set<CommandLine::StringType>* out_difference) {
   std::set<CommandLine::StringType> new_flags =
       ExtractFlagsFromCommandLine(new_cmdline);
   std::set<CommandLine::StringType> active_flags =
       ExtractFlagsFromCommandLine(active_cmdline);
 
+  bool result = false;
   // Needed because std::equal doesn't check if the 2nd set is empty.
-  if (new_flags.size() != active_flags.size())
-    return false;
+  if (new_flags.size() == active_flags.size()) {
+    result =
+        std::equal(new_flags.begin(), new_flags.end(), active_flags.begin());
+  }
 
-  return std::equal(new_flags.begin(), new_flags.end(), active_flags.begin());
+  if (out_difference && !result) {
+    std::set_symmetric_difference(
+        new_flags.begin(),
+        new_flags.end(),
+        active_flags.begin(),
+        active_flags.end(),
+        std::inserter(*out_difference, out_difference->begin()));
+  }
+
+  return result;
 }
 
 void GetFlagsExperimentsData(FlagsStorage* flags_storage,
                              FlagAccess access,
                              base::ListValue* supported_experiments,
                              base::ListValue* unsupported_experiments) {
   std::set<std::string> enabled_experiments;
   GetSanitizedEnabledFlags(flags_storage, &enabled_experiments);
 
   int current_platform = GetCurrentPlatform();
@@ skipping 87 matching lines @@
     action += *it;
     content::RecordComputedAction(action);
   }
   // Since flag metrics are recorded every startup, add a tick so that the
   // stats can be made meaningful.
   if (flags.size())
     content::RecordAction(UserMetricsAction("AboutFlags_StartupTick"));
   content::RecordAction(UserMetricsAction("StartupTick"));
 }
 
+uint32_t GetSwitchUMAId(const std::string& switch_name) {
+  return static_cast<uint32_t>(metrics::HashMetricName(switch_name));
+}
+
+void ReportCustomFlags(const std::string& uma_histogram_hame,
+                       const std::set<std::string>& command_line_difference) {
+  for (std::set<std::string>::const_iterator it =
+           command_line_difference.begin();
+       it != command_line_difference.end();
+       ++it) {
+    int uma_id = about_flags::kBadSwitchFormatHistogramId;
+    if (StartsWithASCII(*it, "--", true /* case_sensitive */)) {
+      // Skip '--' before switch name.
+      std::string switch_name(it->substr(2));
+
+      // Kill value, if any.
+      const size_t value_pos = switch_name.find('=');
+      if (value_pos != std::string::npos)
+        switch_name.resize(value_pos);
+
+      uma_id = GetSwitchUMAId(switch_name);
+    } else {
+      NOTREACHED() << "ReportCustomFlags(): flag '" << *it
+                   << "' has incorrect format.";
+    }
+    DVLOG(1) << "ReportCustomFlags(): histogram='" << uma_histogram_hame
+             << "' '" << *it << "', uma_id=" << uma_id;
+
+    // Sparse histogram macro does not cache the histogram, so it's safe
+    // to use macro with non-static histogram name here.
+    UMA_HISTOGRAM_SPARSE_SLOWLY(uma_histogram_hame, uma_id);
+  }
+}
+
 //////////////////////////////////////////////////////////////////////////////
 // FlagsState implementation.
 
 namespace {
 
 typedef std::map<std::string, std::pair<std::string, std::string> >
     NameToSwitchAndValueMap;
 
 void SetFlagToSwitchMapping(const std::string& key,
                             const std::string& switch_name,
@@ skipping 179 matching lines @@
 }
 
 const Experiment* GetExperiments(size_t* count) {
   *count = num_experiments;
   return experiments;
 }
 
 }  // namespace testing
 
 }  // namespace about_flags