ART: Change InstructionSetFeatures to return unique_ptr

This makes clear the ownership of the object.

Test: m test-art-host
Change-Id: I55fa734f04bc3046d370f4dcf98ce6b17c59e234
diff --git a/compiler/common_compiler_test.cc b/compiler/common_compiler_test.cc
index 51bf9ea..2f9164c 100644
--- a/compiler/common_compiler_test.cc
+++ b/compiler/common_compiler_test.cc
@@ -156,7 +156,7 @@
 
     const InstructionSet instruction_set = kRuntimeISA;
     // Take the default set of instruction features from the build.
-    instruction_set_features_.reset(InstructionSetFeatures::FromCppDefines());
+    instruction_set_features_ = InstructionSetFeatures::FromCppDefines();
 
     runtime_->SetInstructionSet(instruction_set);
     for (int i = 0; i < Runtime::kLastCalleeSaveType; i++) {
diff --git a/compiler/jit/jit_compiler.cc b/compiler/jit/jit_compiler.cc
index c398703..f83d37c 100644
--- a/compiler/jit/jit_compiler.cc
+++ b/compiler/jit/jit_compiler.cc
@@ -124,30 +124,30 @@
     if (option.starts_with("--instruction-set-variant=")) {
       StringPiece str = option.substr(strlen("--instruction-set-variant=")).data();
       VLOG(compiler) << "JIT instruction set variant " << str;
-      instruction_set_features_.reset(InstructionSetFeatures::FromVariant(
-          instruction_set, str.as_string(), &error_msg));
+      instruction_set_features_ = InstructionSetFeatures::FromVariant(
+          instruction_set, str.as_string(), &error_msg);
       if (instruction_set_features_ == nullptr) {
         LOG(WARNING) << "Error parsing " << option << " message=" << error_msg;
       }
     } else if (option.starts_with("--instruction-set-features=")) {
       StringPiece str = option.substr(strlen("--instruction-set-features=")).data();
       VLOG(compiler) << "JIT instruction set features " << str;
-      if (instruction_set_features_.get() == nullptr) {
-        instruction_set_features_.reset(InstructionSetFeatures::FromVariant(
-            instruction_set, "default", &error_msg));
+      if (instruction_set_features_ == nullptr) {
+        instruction_set_features_ = InstructionSetFeatures::FromVariant(
+            instruction_set, "default", &error_msg);
         if (instruction_set_features_ == nullptr) {
           LOG(WARNING) << "Error parsing " << option << " message=" << error_msg;
         }
       }
-      instruction_set_features_.reset(
-          instruction_set_features_->AddFeaturesFromString(str.as_string(), &error_msg));
+      instruction_set_features_ =
+          instruction_set_features_->AddFeaturesFromString(str.as_string(), &error_msg);
       if (instruction_set_features_ == nullptr) {
         LOG(WARNING) << "Error parsing " << option << " message=" << error_msg;
       }
     }
   }
   if (instruction_set_features_ == nullptr) {
-    instruction_set_features_.reset(InstructionSetFeatures::FromCppDefines());
+    instruction_set_features_ = InstructionSetFeatures::FromCppDefines();
   }
   cumulative_logger_.reset(new CumulativeLogger("jit times"));
   compiler_driver_.reset(new CompilerDriver(
diff --git a/compiler/oat_test.cc b/compiler/oat_test.cc
index fd1b135..64ee574 100644
--- a/compiler/oat_test.cc
+++ b/compiler/oat_test.cc
@@ -92,7 +92,7 @@
                      const std::vector<std::string>& compiler_options,
                      /*out*/std::string* error_msg) {
     ASSERT_TRUE(error_msg != nullptr);
-    insn_features_.reset(InstructionSetFeatures::FromVariant(insn_set, "default", error_msg));
+    insn_features_ = InstructionSetFeatures::FromVariant(insn_set, "default", error_msg);
     ASSERT_TRUE(insn_features_ != nullptr) << error_msg;
     compiler_options_.reset(new CompilerOptions);
     for (const std::string& option : compiler_options) {
diff --git a/compiler/optimizing/optimizing_cfi_test.cc b/compiler/optimizing/optimizing_cfi_test.cc
index bacf994..013e110 100644
--- a/compiler/optimizing/optimizing_cfi_test.cc
+++ b/compiler/optimizing/optimizing_cfi_test.cc
@@ -52,7 +52,7 @@
   void SetUpFrame(InstructionSet isa) {
     // Setup simple context.
     std::string error;
-    isa_features_.reset(InstructionSetFeatures::FromVariant(isa, "default", &error));
+    isa_features_ = InstructionSetFeatures::FromVariant(isa, "default", &error);
     graph_ = CreateGraph(&allocator_);
     // Generate simple frame with some spills.
     code_gen_ = CodeGenerator::Create(graph_, isa, *isa_features_, opts_);