Remove the enable_task_manager build flag and define.

chrome/browser/extensions/BUILD.gn

Index: chrome/browser/extensions/BUILD.gn
diff --git a/chrome/browser/extensions/BUILD.gn b/chrome/browser/extensions/BUILD.gn
index c647868f4bc8ce46062c624af055646afce4c9de..afc16da6be8657063bb3e66d137477415336f1cb 100644
--- a/chrome/browser/extensions/BUILD.gn
+++ b/chrome/browser/extensions/BUILD.gn
@@ -1050,9 +1050,11 @@ static_library("extensions") {
     }
   }
 
-  if (!is_android && !is_ios) {
-    # Non-mobile.
-    #deps += [ "//apps" ]
+  if (!is_android) {
+    sources += [
+      "api/processes/processes_api.cc",
+      "api/processes/processes_api.h",
+    ]
   }
 
   if (is_win || is_mac) {
@@ -1140,13 +1142,6 @@ static_library("extensions") {
     ]
   }
 
-  if (enable_task_manager) {
-    sources += [
-      "api/processes/processes_api.cc",
-      "api/processes/processes_api.h",
-    ]
-  }
-
   if (enable_rlz_support) {
     deps += [ "//rlz:rlz_lib" ]
   }