Add support for the ExperimentalSwReporterEngine field trial.

chrome/browser/component_updater/sw_reporter_installer_win.cc

Index: chrome/browser/component_updater/sw_reporter_installer_win.cc
diff --git a/chrome/browser/component_updater/sw_reporter_installer_win.cc b/chrome/browser/component_updater/sw_reporter_installer_win.cc
index cad962c7d29a8f83f4a2a8fb84770271fee87a19..041ec53f64f7f84f8e0f3302dac46ef7e7a3e2bc 100644
--- a/chrome/browser/component_updater/sw_reporter_installer_win.cc
+++ b/chrome/browser/component_updater/sw_reporter_installer_win.cc
@@ -6,6 +6,7 @@
 
 #include <stdint.h>
 
+#include <algorithm>
 #include <map>
 #include <memory>
 #include <string>
@@ -14,6 +15,8 @@
 
 #include "base/base_paths.h"
 #include "base/bind.h"
+#include "base/command_line.h"
+#include "base/feature_list.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/logging.h"
@@ -21,10 +24,12 @@
 #include "base/metrics/sparse_histogram.h"
 #include "base/path_service.h"
 #include "base/strings/string_tokenizer.h"
+#include "base/strings/string_util.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/threading/worker_pool.h"
 #include "base/time/time.h"
 #include "base/win/registry.h"
+#include "base/win/windows_version.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/safe_browsing/srt_fetcher_win.h"
 #include "chrome/browser/safe_browsing/srt_field_trial_win.h"
@@ -35,14 +40,15 @@
 #include "components/prefs/pref_registry_simple.h"
 #include "components/update_client/update_client.h"
 #include "components/update_client/utils.h"
+#include "components/variations/variations_associated_data.h"
 #include "content/public/browser/browser_thread.h"
 
 namespace component_updater {
 
 namespace {
 
-// These two sets of values are used to send UMA information and are replicated
-// in the histograms.xml file, so the order MUST NOT CHANGE.
+// These values are used to send UMA information and are replicated in the
+// histograms.xml file, so the order MUST NOT CHANGE.
 enum SRTCompleted {
   SRT_COMPLETED_NOT_YET = 0,
   SRT_COMPLETED_YES = 1,
@@ -117,11 +123,134 @@ void RunSwReporterAfterStartup(
                  base::WorkerPool::GetTaskRunner(true)));
 }
 
+// Constants and helper functions for the Experimental Engine feature.
+
+constexpr base::Feature kExperimentalEngineFeature{
+    "ExperimentalSwReporterEngine", base::FEATURE_DISABLED_BY_DEFAULT};
+
+// Max length of an installer attribute (taken from the regexp in
+// ComponentInstallerTraits::InstallerAttributes).
+constexpr size_t kMaxAttributeLength = 256;
+
+// Max length of the registry and histogram suffix. Fairly arbitrary: the
+// Windows registry accepts much longer keys, but we need to display this
+// string in histograms as well.
+constexpr size_t kMaxSuffixLength = 80;
+
+// These MUST match the values for SwReporterExperimentError in histograms.xml.
+enum ExperimentError {
+  EXPERIMENT_ERROR_BAD_TAG = 0,
+  EXPERIMENT_ERROR_BAD_PARAMS = 1,
+  EXPERIMENT_ERROR_MAX,
+};
+
+void ReportExperimentError(ExperimentError error) {
+  UMA_HISTOGRAM_ENUMERATION("SoftwareReporter.ExperimentErrors", error,
+                            EXPERIMENT_ERROR_MAX);
+}
+
+// Ensures |str| contains only alphanumeric characters and characters from
+// |extras|, and is not longer than |max_length|.
+bool ValidateString(const std::string& str,
+                    const std::string& extras,
+                    size_t max_length) {
+  return str.size() <= max_length &&
+         std::all_of(str.cbegin(), str.cend(), [&extras](char c) {
+           return base::IsAsciiAlpha(c) || base::IsAsciiDigit(c) ||
+                  extras.find(c) != std::string::npos;
+         });
+}
+
+// Reads the command-line params and an UMA histogram suffix from the manifest,
+// and launch the SwReporter with those parameters. If anything goes wrong the
+// SwReporter should not be run at all, instead of falling back to the default.
+void RunExperimentalSwReporter(const base::FilePath& exe_path,
+                               const base::Version& version,
+                               std::unique_ptr<base::DictionaryValue> manifest,
+                               const SwReporterRunner& reporter_runner) {
+  // Don't log an error if the launch_params section is entirely missing.  This
+  // can happen when the user already has an older version of the software
+  // reporter component, so |ComponentReady| is called on startup before the
+  // experimental version is downloaded.
+  //
+  // Also don't run the old version, though. We want this user to run the
+  // experimental version once it's been downloaded.
+  base::Value* launch_params = nullptr;
+  if (!manifest->Get("launch_params", &launch_params))
+    return;
+
+  const base::ListValue* parameter_list = nullptr;
+  if (!launch_params->GetAsList(&parameter_list) || parameter_list->empty()) {
+    ReportExperimentError(EXPERIMENT_ERROR_BAD_PARAMS);
+    return;
+  }
+
+  // For now we only support running the reporter once, so only look at the
+  // first set of arguments in the list.
+  const base::DictionaryValue* invocation_params = nullptr;
+  if (!parameter_list->GetDictionary(0, &invocation_params)) {
+    ReportExperimentError(EXPERIMENT_ERROR_BAD_PARAMS);
+    return;
+  }
+
+  // The suffix is optional. If present, it must be a short alphanumeric string.
+  std::string suffix;
+  const base::Value* suffix_value = nullptr;
+  if (invocation_params->Get("suffix", &suffix_value)) {
+    if (!suffix_value->GetAsString(&suffix)) {
+      ReportExperimentError(EXPERIMENT_ERROR_BAD_PARAMS);
+      return;
+    }
+    if (!suffix.empty() &&
+        !ValidateString(suffix, std::string(), kMaxSuffixLength)) {
+      ReportExperimentError(EXPERIMENT_ERROR_BAD_PARAMS);
+      return;
+    }
+  }
+
+  // Build a command line for the reporter out of the executable path and the
+  // (optional) arguments from the manifest.
+  std::vector<base::string16> argv = {exe_path.value()};
+  const base::Value* arguments_value = nullptr;
+  if (invocation_params->Get("arguments", &arguments_value)) {
+    const base::ListValue* arguments = nullptr;
+    if (!arguments_value->GetAsList(&arguments)) {
+      ReportExperimentError(EXPERIMENT_ERROR_BAD_PARAMS);
+      return;
+    }
+    for (const std::unique_ptr<base::Value>& value : *arguments) {
+      base::string16 argument;
+      if (!value->GetAsString(&argument)) {
+        ReportExperimentError(EXPERIMENT_ERROR_BAD_PARAMS);
+        return;
+      }
+      if (!argument.empty())
+        argv.push_back(argument);
+    }
+  }
+  base::CommandLine command_line(argv);
+
+  // Add the histogram suffix to the command-line as well, so that the
+  // reporter will add the same suffix to registry keys where it writes
+  // metrics.
+  if (!suffix.empty())
+    command_line.AppendSwitchASCII("registry-suffix", suffix);
+
+  auto invocation =
+      safe_browsing::SwReporterInvocation::FromCommandLine(command_line);
+  invocation.suffix = suffix;
+  invocation.is_experimental = true;
+
+  reporter_runner.Run(invocation, version);
+}
+
 }  // namespace
 
 SwReporterInstallerTraits::SwReporterInstallerTraits(
-    const SwReporterRunner& reporter_runner)
-    : reporter_runner_(reporter_runner) {}
+    const SwReporterRunner& reporter_runner,
+    bool is_experimental_engine_supported)
+    : reporter_runner_(reporter_runner),
+      is_experimental_engine_supported_(is_experimental_engine_supported) {}
 
 SwReporterInstallerTraits::~SwReporterInstallerTraits() {}
 
@@ -152,6 +281,11 @@ void SwReporterInstallerTraits::ComponentReady(
     std::unique_ptr<base::DictionaryValue> manifest) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   const base::FilePath exe_path(install_dir.Append(kSwReporterExeName));
+  if (IsExperimentalEngineEnabled()) {
+    RunExperimentalSwReporter(exe_path, version, std::move(manifest),
+                              reporter_runner_);
+    return;
+  }
   reporter_runner_.Run(
       safe_browsing::SwReporterInvocation::FromFilePath(exe_path), version);
 }
@@ -171,13 +305,36 @@ std::string SwReporterInstallerTraits::GetName() const {
 
 update_client::InstallerAttributes
 SwReporterInstallerTraits::GetInstallerAttributes() const {
-  return update_client::InstallerAttributes();
+  update_client::InstallerAttributes attributes;
+  if (IsExperimentalEngineEnabled()) {
+    // Pass the "tag" parameter to the installer; it will be used to choose
+    // which binary is downloaded.
+    constexpr char kTagParam[] = "tag";
+    const std::string tag = variations::GetVariationParamValueByFeature(
+        kExperimentalEngineFeature, kTagParam);
+
+    // If the tag is not a valid attribute (see the regexp in
+    // ComponentInstallerTraits::InstallerAttributes), set it to a valid but
+    // unrecognized value so that nothing will be downloaded.
+    if (tag.empty() || !ValidateString(tag, "_.,;+_=", kMaxAttributeLength)) {
+      ReportExperimentError(EXPERIMENT_ERROR_BAD_TAG);
+      attributes[kTagParam] = "missing_tag";
+    } else {
+      attributes[kTagParam] = tag;
+    }
+  }
+  return attributes;
 }
 
 std::vector<std::string> SwReporterInstallerTraits::GetMimeTypes() const {
   return std::vector<std::string>();
 }
 
+bool SwReporterInstallerTraits::IsExperimentalEngineEnabled() const {
+  return is_experimental_engine_supported_ &&
+         base::FeatureList::IsEnabled(kExperimentalEngineFeature);
+}
+
 void RegisterSwReporterComponent(ComponentUpdateService* cus) {
   if (!safe_browsing::IsSwReporterEnabled())
     return;
@@ -254,9 +411,16 @@ void RegisterSwReporterComponent(ComponentUpdateService* cus) {
     }
   }
 
+  // The experiment is only enabled on x86. There's no way to check this in the
+  // variations config so we'll hard-code it.
+  const bool is_experimental_engine_enabled =
+      base::win::OSInfo::GetInstance()->architecture() ==
+      base::win::OSInfo::X86_ARCHITECTURE;
+
   // Install the component.
   std::unique_ptr<ComponentInstallerTraits> traits(
-      new SwReporterInstallerTraits(base::Bind(&RunSwReporterAfterStartup)));
+      new SwReporterInstallerTraits(base::Bind(&RunSwReporterAfterStartup),
+                                    is_experimental_engine_enabled));
   // |cus| will take ownership of |installer| during installer->Register(cus).
   DefaultComponentInstaller* installer =
       new DefaultComponentInstaller(std::move(traits));