Add record-as-much-as-possible mode for about://tracing.

Update DEPS for trace-viewer to include the 3 tracing modes selector.

BUG=396081
TEST=

Review URL: https://codereview.chromium.org/1033223008

Cr-Commit-Position: refs/heads/master@{#322689}

DEPS

@@ -132,7 +132,7 @@ deps = {
    Var('chromium_git') + '/crashpad/crashpad.git' + '@' + '5d0a133ecd6625f30c6491d502f12f26a0bef32d',
 
   'src/third_party/trace-viewer':
-   Var('chromium_git') + '/external/trace-viewer.git' + '@' + 'ff20313e37892c3c7f20c88bb22ab6f6e65659ae',
+   Var('chromium_git') + '/external/trace-viewer.git' + '@' + '31e508019823eb4846821b61ad492e3ea7483d71',
 
   'src/third_party/WebKit':
    Var('chromium_git') + '/chromium/blink.git' + '@' +  Var('webkit_revision'),

content/browser/tracing/tracing_ui.cc

@@ -86,20 +86,16 @@ bool GetTracingOptions(const std::string& data64,
   options_ok &= options->GetString("categoryFilter", &category_filter_string);
   *category_filter = base::trace_event::CategoryFilter(category_filter_string);
 
+  std::string record_mode;
+  options_ok &=
+      options->GetString("tracingRecordMode", &record_mode);
+  options_ok &= tracing_options->SetFromString(record_mode);
+
   options_ok &= options->GetBoolean("useSystemTracing",
                                     &tracing_options->enable_systrace);
   options_ok &=
       options->GetBoolean("useSampling", &tracing_options->enable_sampling);
 
-  bool use_continuous_tracing;
-  options_ok &=
-      options->GetBoolean("useContinuousTracing", &use_continuous_tracing);
-
-  if (use_continuous_tracing)
-    tracing_options->record_mode = base::trace_event::RECORD_CONTINUOUSLY;
-  else
-    tracing_options->record_mode = base::trace_event::RECORD_UNTIL_FULL;
-
   if (!options_ok) {
     LOG(ERROR) << "Malformed options";
     return false;