[MTE] Add MemoryTaggingDogfood synthetic Finch

MemoryTaggingDogfood synthetic Finch group will be:
- unset if kPartitionAllocMemoryTagging is not enabled
- Disabled if MTE bootloader flag is disabled (or MTE is not available)
- Enabled if MTE is enabled

(cherry picked from commit 592865e)

Bug: 1448009
Change-Id: Id879838c67d8c8bdec98b4562a54c71ae635ed8b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4583313
Commit-Queue: Keishi Hattori <keishi@chromium.org>
Reviewed-by: Bartek Nowierski <bartekn@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1152574}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4596638
Auto-Submit: Keishi Hattori <keishi@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/5790@{#447}
Cr-Branched-From: 1d71a33-refs/heads/main@{#1148114}

base/allocator/partition_alloc_support.cc

@@ -423,6 +423,17 @@ std::map<std::string, std::string> ProposeSyntheticFinchTrials() {
   trials.emplace(base::features::kRendererLiveBRPSyntheticTrialName, "Control");
 #endif
 
+#if PA_CONFIG(HAS_MEMORY_TAGGING)
+  if (base::FeatureList::IsEnabled(
+          base::features::kPartitionAllocMemoryTagging)) {
+    if (base::CPU::GetInstanceNoAllocation().has_mte()) {
+      trials.emplace("MemoryTaggingDogfood", "Enabled");
+    } else {
+      trials.emplace("MemoryTaggingDogfood", "Disabled");
+    }
+  }
+#endif
+
   return trials;
 }
 
@@ -891,6 +902,12 @@ void PartitionAllocSupport::ReconfigureForTests() {
 // static
 bool PartitionAllocSupport::ShouldEnableMemoryTagging(
     const std::string& process_type) {
+  // Check kPartitionAllocMemoryTagging first so the Feature is activated even
+  // when mte bootloader flag is disabled.
+  if (!base::FeatureList::IsEnabled(
+          base::features::kPartitionAllocMemoryTagging)) {
+    return false;
+  }
   if (!base::CPU::GetInstanceNoAllocation().has_mte()) {
     return false;
   }
@@ -900,10 +917,6 @@ bool PartitionAllocSupport::ShouldEnableMemoryTagging(
           base::features::kKillPartitionAllocMemoryTagging)) {
     return false;
   }
-  if (!base::FeatureList::IsEnabled(
-          base::features::kPartitionAllocMemoryTagging)) {
-    return false;
-  }
   switch (base::features::kMemoryTaggingEnabledProcessesParam.Get()) {
     case base::features::MemoryTaggingEnabledProcesses::kBrowserOnly:
       return process_type.empty();

base/allocator/partition_alloc_support_unittest.cc

@@ -10,6 +10,7 @@
 
 #include "base/allocator/partition_alloc_features.h"
 #include "base/allocator/partition_allocator/dangling_raw_ptr_checks.h"
+#include "base/allocator/partition_allocator/partition_alloc_base/cpu.h"
 #include "base/allocator/partition_allocator/partition_alloc_buildflags.h"
 #include "base/feature_list.h"
 #include "base/task/single_thread_task_runner.h"
@@ -419,5 +420,36 @@ TEST(PartitionAllocSupportTest,
 #endif
 }
 
+#if PA_CONFIG(HAS_MEMORY_TAGGING)
+TEST(PartitionAllocSupportTest,
+     ProposeSyntheticFinchTrials_MemoryTaggingDogfood) {
+  {
+    test::ScopedFeatureList scope;
+    scope.InitWithFeatures({}, {features::kPartitionAllocMemoryTagging});
+
+    auto trials = ProposeSyntheticFinchTrials();
+
+    auto group_iter = trials.find("MemoryTaggingDogfood");
+    EXPECT_EQ(group_iter, trials.end());
+  }
+
+  {
+    test::ScopedFeatureList scope;
+    scope.InitWithFeatures({features::kPartitionAllocMemoryTagging}, {});
+
+    auto trials = ProposeSyntheticFinchTrials();
+
+    std::string expectation =
+        partition_alloc::internal::base::CPU::GetInstanceNoAllocation()
+                .has_mte()
+            ? "Enabled"
+            : "Disabled";
+    auto group_iter = trials.find("MemoryTaggingDogfood");
+    EXPECT_NE(group_iter, trials.end());
+    EXPECT_EQ(group_iter->second, expectation);
+  }
+}
+#endif
+
 }  // namespace allocator
 }  // namespace base