Set up Finch trial for malware download warnings

chrome/browser/download/download_danger_prompt.cc

Index: chrome/browser/download/download_danger_prompt.cc
diff --git a/chrome/browser/download/download_danger_prompt.cc b/chrome/browser/download/download_danger_prompt.cc
index fc0948dca247540165adb01571a1bfd7fdcbe72d..4ad36175fa6ed032c6f061cd209c47b30da94b25 100644
--- a/chrome/browser/download/download_danger_prompt.cc
+++ b/chrome/browser/download/download_danger_prompt.cc
@@ -5,8 +5,10 @@
 #include "chrome/browser/download/download_danger_prompt.h"
 
 #include "base/bind.h"
+#include "base/metrics/field_trial.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/download/chrome_download_manager_delegate.h"
+#include "chrome/browser/download/download_util.h"
 #include "chrome/browser/ui/tab_modal_confirm_dialog.h"
 #include "chrome/browser/ui/tab_modal_confirm_dialog_delegate.h"
 #include "content/public/browser/download_danger_type.h"
@@ -102,6 +104,8 @@ string16 DownloadDangerPromptImpl::GetMessage() {
   if (!show_context_)
     return l10n_util::GetStringUTF16(
         IDS_PROMPT_CONFIRM_KEEP_DANGEROUS_DOWNLOAD);
+  std::string trial_condition =
+      base::FieldTrialList::FindFullName(download_util::kFinchTrialName);
   switch (download_->GetDangerType()) {
     case content::DOWNLOAD_DANGER_TYPE_DANGEROUS_FILE:
       return l10n_util::GetStringFUTF16(
@@ -110,9 +114,15 @@ string16 DownloadDangerPromptImpl::GetMessage() {
     case content::DOWNLOAD_DANGER_TYPE_DANGEROUS_URL: // Fall through
     case content::DOWNLOAD_DANGER_TYPE_DANGEROUS_CONTENT:
     case content::DOWNLOAD_DANGER_TYPE_DANGEROUS_HOST:
-      return l10n_util::GetStringFUTF16(
-          IDS_PROMPT_MALICIOUS_DOWNLOAD_CONTENT,
-          download_->GetFileNameToReportUser().LossyDisplayName());
+      if (trial_condition.empty()) {
+        return l10n_util::GetStringFUTF16(
+            IDS_PROMPT_MALICIOUS_DOWNLOAD_CONTENT,
+            download_->GetFileNameToReportUser().LossyDisplayName());
+      } else {
+        return download_util::AssembleMalwareFinchString(
+            trial_condition,
+            download_->GetFileNameToReportUser().LossyDisplayName());
+      }
     case content::DOWNLOAD_DANGER_TYPE_UNCOMMON_CONTENT:
       return l10n_util::GetStringFUTF16(
           IDS_PROMPT_UNCOMMON_DOWNLOAD_CONTENT,