Enable PRE_ test in content_browsertests in android-oreo-x86-rel and
android-pie-arm64-rel.

Instead of enabling this flag for the whole builder, we can enable it
on gtest related test suite only.

PRE_ tests are executed in content_browsertests as expected:
https://screenshot.googleplex.com/7XvkjbWuXWRJGgE

Bug: 1257820
Change-Id: I24ab282813f69da487399ef890b30e19419060ff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5294854
Commit-Queue: James Shen <zhiyuans@google.com>
Reviewed-by: Haiyang Pan <hypan@google.com>
Cr-Commit-Position: refs/heads/main@{#1260639}

diff --git a/testing/buildbot/chromium.android.json b/testing/buildbot/chromium.android.json
index 1cacd9c..fe8cf91 100644
--- a/testing/buildbot/chromium.android.json
+++ b/testing/buildbot/chromium.android.json

@@ -31512,6 +31512,7 @@
           "--gs-results-bucket=chromium-result-details",
           "--recover-devices",
           "--avd-config=../../tools/android/avd/proto/generic_android26.textpb",
+          "--gtest-also-run-pre-tests",
           "--test-launcher-filter-file=../../testing/buildbot/filters/android.emulator_o.content_browsertests.filter"
         ],
         "isolate_profile_data": true,
@@ -35787,6 +35788,7 @@
           "--use-persistent-shell",
           "--gs-results-bucket=chromium-result-details",
           "--recover-devices",
+          "--gtest-also-run-pre-tests",
           "--test-launcher-filter-file=../../testing/buildbot/filters/android.pie_arm64.content_browsertests_coverage.filter"
         ],
         "isolate_profile_data": true,

diff --git a/testing/buildbot/test_suite_exceptions.pyl b/testing/buildbot/test_suite_exceptions.pyl
index 321a4c4..abcf5ea 100644
--- a/testing/buildbot/test_suite_exceptions.pyl
+++ b/testing/buildbot/test_suite_exceptions.pyl

@@ -2014,6 +2014,7 @@
       # If you change this, make similar changes in android-x86-code-coverage below
       'android-oreo-x86-rel': {
         'args': [
+          '--gtest-also-run-pre-tests',
           '--test-launcher-filter-file=../../testing/buildbot/filters/android.emulator_o.content_browsertests.filter',
         ],
         'swarming': {
@@ -2026,6 +2027,7 @@
       },
       'android-pie-arm64-rel': {
         'args': [
+          '--gtest-also-run-pre-tests',
           '--test-launcher-filter-file=../../testing/buildbot/filters/android.pie_arm64.content_browsertests_coverage.filter',
         ],
         # Only retry the individual failed tests instead of rerunning entire