Enable by default drive search on all channels and LSP API on dev.

In M45, drive search is enabled by default on all channels and launcher
search provider is enabled by default only on dev channel.
We'll add two flags to disable these features respectively.
These flags are independent and don't affect each other, i.e. turing on
--disable-launcher-search-provider-api does not disable drive search.

Note: While we also need to update _permission_features.json to make LSP
available on Dev channel, we'll do it with another CL after the install
time permission message of LSP has been decided.

BUG=502097
TEST=none

Review URL: https://codereview.chromium.org/1197563002

Cr-Commit-Position: refs/heads/master@{#335885}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 65c98d2..97acc29 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -1896,14 +1896,19 @@
      kOsAll,
      SINGLE_VALUE_TYPE(switches::kEnableMediaRouter)},
 #endif  // defined(ENABLE_MEDIA_ROUTER)
-// Since kEnableLauncherSearchProviderApi is not available when app list is
-// disabled, flag guard enable-launcher-search-provider-api.
+// Since kDisableDriveSearchInAppLauncher and kDisableLauncherSearchProviderAPI
+// are not available when app list is disabled, flag guard them.
 #if defined(ENABLE_APP_LIST)
-    {"enable-launcher-search-provider-api",
-     IDS_FLAGS_ENABLE_LAUNCHER_SEARCH_PROVIDER_API,
-     IDS_FLAGS_ENABLE_LAUNCHER_SEARCH_PROVIDER_API_DESCRIPTION,
+    {"disable-drive-search-in-app-launcher",
+     IDS_FLAGS_DISABLE_DRIVE_SEARCH_IN_APP_LAUNCHER,
+     IDS_FLAGS_DISABLE_DRIVE_SEARCH_IN_APP_LAUNCHER_DESCRIPTION,
      kOsCrOS,
-     SINGLE_VALUE_TYPE(app_list::switches::kEnableLauncherSearchProviderApi)},
+     SINGLE_VALUE_TYPE(app_list::switches::kDisableDriveSearchInAppLauncher)},
+    {"disable-launcher-search-provider-api",
+     IDS_FLAGS_DISABLE_LAUNCHER_SEARCH_PROVIDER_API,
+     IDS_FLAGS_DISABLE_LAUNCHER_SEARCH_PROVIDER_API_DESCRIPTION,
+     kOsCrOS,
+     SINGLE_VALUE_TYPE(app_list::switches::kDisableLauncherSearchProviderApi)},
 #endif  // defined(ENABLE_APP_LIST)
 #if defined(OS_CHROMEOS)
     {"disable-mtp-write-support",