Add a flag for parallel download feature in chrome://flags.

This CL adds a flag for parallel download feature.

This feature also has a finch experiment.

Doc: go/chrome-parallel-download.

Bug: 763039
Change-Id: Id6dbec1c25f430439f3967060b52c2a54f88985b
Reviewed-on: https://chromium-review.googlesource.com/656301
Commit-Queue: Xing Liu <[email protected]>
Reviewed-by: Min Qin <[email protected]>
Cr-Commit-Position: refs/heads/master@{#502389}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index ac5ee6f..0773c2e 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -3492,6 +3492,10 @@
          ash::switches::kAshDisableTabletAutohideTitlebars)},
 #endif  // defined(OS_CHROMEOS)
 
+    {"enable-parallel-downloading", flag_descriptions::kParallelDownloadingName,
+     flag_descriptions::kParallelDownloadingDescription, kOsAll,
+     FEATURE_VALUE_TYPE(features::kParallelDownloading)},
+
     // NOTE: Adding new command-line switches requires adding corresponding
     // entries to enum "LoginCustomFlags" in histograms/enums.xml. See note in
     // enums.xml and don't forget to run AboutFlagsHistogramTest unit test.
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index 6254a58..f4535b8 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -985,6 +985,11 @@
 const char kOverscrollStartThreshold166Percent[] = "166%";
 const char kOverscrollStartThreshold200Percent[] = "200%";
 
+const char kParallelDownloadingName[] = "Parallel downloading";
+const char kParallelDownloadingDescription[] =
+    "Enable parallel downloading to"
+    "accelerate download speed.";
+
 const char kPassiveEventListenerDefaultName[] =
     "Passive Event Listener Override";
 const char kPassiveEventListenerDefaultDescription[] =
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index 2efb442..d6ff3e6b 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -614,6 +614,9 @@
 extern const char kOverscrollStartThreshold166Percent[];
 extern const char kOverscrollStartThreshold200Percent[];
 
+extern const char kParallelDownloadingName[];
+extern const char kParallelDownloadingDescription[];
+
 extern const char kPassiveEventListenerDefaultName[];
 extern const char kPassiveEventListenerDefaultDescription[];
 extern const char kPassiveEventListenerTrue[];