desktop-pwas: Disable link capturing by default

After this patch, Desktop PWAs should no longer capture links without
users enable the kDesktopPWAsLinkCapturing flag.

Final patch to disable link capturing by default:

[1] Specify that throttle and tests are for experimental feature
    (https://crrev.com/ba5d9af)
[2] Extract tests that should run when link capturing is off
    (https://crrev.com/e3aa04a)
[3] Handle out-of-scope navigations and stop link capturing by
    default (https://crrev.com/c/942597)
[4] Disable link capturing by default (This patch)

Bug: 814102
Change-Id: I0d03c93c2594c3da7d5139496502244e299c8e84
Reviewed-on: https://chromium-review.googlesource.com/950484Reviewed-by: Matt Giuca <mgiuca@chromium.org>
Commit-Queue: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541711}

chrome/common/chrome_features.cc

@@ -186,8 +186,8 @@ const base::Feature kDesktopPWAWindowing{"DesktopPWAWindowing",
                                          base::FEATURE_DISABLED_BY_DEFAULT};
 
 // Enables or disables Desktop PWAs capturing links.
-const base::Feature kDesktopPWAsLinkCapturing{"DesktopPWAsLinkCapturing",
-                                              base::FEATURE_ENABLED_BY_DEFAULT};
+const base::Feature kDesktopPWAsLinkCapturing{
+    "DesktopPWAsLinkCapturing", base::FEATURE_DISABLED_BY_DEFAULT};
 
 #if !defined(OS_ANDROID)
 const base::Feature kDoodlesOnLocalNtp{"DoodlesOnLocalNtp",