[PA] Get rid off USE_PARTITION_ALLOC_EVERYWHERE

We already have USE_PARTITION_ALLOC_AS_MALLOC, which serves the same
purpose.

Change-Id: I689386a830115a4b1c5632b4e75639365e57d996
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2631893Reviewed-by: Sébastien Marchand <sebmarchand@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Ilya Sherman <isherman@chromium.org>
Auto-Submit: Bartek Nowierski <bartekn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845028}

chrome/browser/BUILD.gn

@@ -84,12 +84,6 @@ buildflag_header("buildflags") {
   if (is_win) {
     flags += [ "ENABLE_SEGMENT_HEAP=$enable_segment_heap" ]
   }
-
-  if (use_allocator == "partition") {
-    flags += [ "USE_PARTITION_ALLOC_EVERYWHERE=1" ]
-  } else {
-    flags += [ "USE_PARTITION_ALLOC_EVERYWHERE=0" ]
-  }
 }
 
 # This proto library is used for non - android NTPs below.

chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc

@@ -551,7 +551,7 @@ void ChromeBrowserMainExtraPartsMetrics::PreBrowserStart() {
   // Records whether or not PartitionAlloc is used as the default allocator.
   ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial(
       "PartitionAllocEverywhere",
-#if BUILDFLAG(USE_PARTITION_ALLOC_EVERYWHERE)
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
       "Enabled"
 #else
       "Disabled"