Added flag in chrome://flags to enable the New Launcher UI.

chrome/browser/flag_descriptions.cc

Index: chrome/browser/flag_descriptions.cc
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index 27a963351a282e3426826dd9d3f41ea2e2e118bd..7271e18b3e2941ee75928db16fff23957479feae 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -2927,6 +2927,12 @@ const char kDisplayColorCalibrationDescription[] =
     "Allow color calibration of the display if the display supports the "
     "feature.";
 
+const char kEnableFullscreenAppListName[] = "Enable The Peeking Launcher";
+
+const char kEnableFullscreenAppListDescription[] =
+    "The new launcher UI supports touch and provides more space for upcoming "
+    "features.";

[stevenjb, 2017/06/30 22:18:58]

'launcher' is fine in these strings, although I have no idea what 'Peeking'
means; presumably folks using this switch will know?

s/The new launcher/The peeking launcher/ ?

[newcomer, 2017/07/11 19:54:05]

Good catch!

+
 const char kMemoryPressureThresholdName[] =
     "Memory discard strategy for advanced pressure handling";