Revert "Remove SoleIntegration flag"

This reverts commit bfd17e5e46cad8a9aa563a627e3d492ef78aa836.

Reason for revert: broke Clank downstream

Original change's description:
> Remove SoleIntegration flag
> 
> Sole integration was launched in M65, and we no longer need this flag.
> 
> Bug: 778805
> Change-Id: I6669a87dcb7a6ff4705a30aaa2cf71d6670a822a
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1578101
> Commit-Queue: Wei-Yin Chen (陳威尹) <[email protected]>
> Reviewed-by: Theresa <[email protected]>
> Cr-Commit-Position: refs/heads/master@{#653718}

[email protected],[email protected]

Change-Id: I9cd3a7f54acb633c6390d4ca0c9d47efa5e8e066
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 778805
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1583064
Reviewed-by: Wei-Yin Chen (陳威尹) <[email protected]>
Commit-Queue: Wei-Yin Chen (陳威尹) <[email protected]>
Cr-Commit-Position: refs/heads/master@{#653741}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index dd7a82c..334f2ce 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -2965,6 +2965,12 @@
      kOsDesktop, FEATURE_VALUE_TYPE(device::kWebAuthPINSupport)},
 #endif  // !defined(OS_ANDROID)
 
+#if defined(OS_ANDROID)
+    {"enable-sole-integration", flag_descriptions::kSoleIntegrationName,
+     flag_descriptions::kSoleIntegrationDescription, kOsAndroid,
+     FEATURE_VALUE_TYPE(chrome::android::kSoleIntegration)},
+#endif  // defined(OS_ANDROID)
+
     {"enable-viz-display-compositor",
      flag_descriptions::kVizDisplayCompositorName,
      flag_descriptions::kVizDisplayCompositorDescription, kOsAndroid | kOsCrOS,