Fix compile error about base_unittests on Loongson.

This CL fixes the build error with the following message:
     ../../base/allocator/partition_allocator/partition_alloc_unittest.cc: In member function ‘virtual void base::internal::PartitionAllocTest_PurgeDiscardable_Test::TestBody()’:
     ../../base/allocator/partition_allocator/partition_alloc_unittest.cc:1905:42: error: ‘PartitionAllocGeneric’ was not declared in this scope
          char* ptr1 = reinterpret_cast<char*>(PartitionAllocGeneric(
                                          ^~~~~~~~~~~~~~~~~~~~~
     ../../base/allocator/partition_allocator/partition_alloc_unittest.cc:1905:42: note: suggested alternative: ‘PartitionAllocatorGeneric’
          char* ptr1 = reinterpret_cast<char*>(PartitionAllocGeneric(
                                          ^~~~~~~~~~~~~~~~~~~~~
                                          PartitionAllocatorGeneric
     ../../base/allocator/partition_allocator/partition_alloc_unittest.cc:1909:5: error: ‘PartitionFreeGeneric’ was not declared in this scope
          PartitionFreeGeneric(generic_allocator.root(), ptr1);

Bug= 859785

R= haraken@chromium.org

Change-Id: I6e06534ba78fa7a3742ec3585502d60943374b1a
Reviewed-on: https://chromium-review.googlesource.com/1123931Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: 汪 清 <wangqing-hf@loongson.cn>
Cr-Commit-Position: refs/heads/master@{#572150}

base/allocator/partition_allocator/partition_alloc_unittest.cc

@@ -1902,19 +1902,16 @@ TEST_F(PartitionAllocTest, PurgeDiscardable) {
 // for clarity of purpose and for applicability to more architectures.
 #if defined(_MIPS_ARCH_LOONGSON)
   {
-    char* ptr1 = reinterpret_cast<char*>(PartitionAllocGeneric(
-        generic_allocator.root(), (32 * kSystemPageSize) - kExtraAllocSize,
-        type_name));
+    char* ptr1 = reinterpret_cast<char*>(generic_allocator.root()->Alloc(
+        (32 * kSystemPageSize) - kExtraAllocSize, type_name));
     memset(ptr1, 'A', (32 * kSystemPageSize) - kExtraAllocSize);
-    PartitionFreeGeneric(generic_allocator.root(), ptr1);
-    ptr1 = reinterpret_cast<char*>(PartitionAllocGeneric(
-        generic_allocator.root(), (31 * kSystemPageSize) - kExtraAllocSize,
-        type_name));
+    generic_allocator.root()->Free(ptr1);
+    ptr1 = reinterpret_cast<char*>(generic_allocator.root()->Alloc(
+        (31 * kSystemPageSize) - kExtraAllocSize, type_name));
     {
       MockPartitionStatsDumper dumper;
-      PartitionDumpStatsGeneric(generic_allocator.root(),
-                                "mock_generic_allocator",
-                                false /* detailed dump */, &dumper);
+      generic_allocator.root()->DumpStats("mock_generic_allocator",
+                                          false /* detailed dump */, &dumper);
       EXPECT_TRUE(dumper.IsMemoryAllocationRecorded());
 
       const PartitionBucketMemoryStats* stats =
@@ -1928,12 +1925,12 @@ TEST_F(PartitionAllocTest, PurgeDiscardable) {
     }
     CheckPageInCore(ptr1 - kPointerOffset + (kSystemPageSize * 30), true);
     CheckPageInCore(ptr1 - kPointerOffset + (kSystemPageSize * 31), true);
-    PartitionPurgeMemoryGeneric(generic_allocator.root(),
-                                PartitionPurgeDiscardUnusedSystemPages);
+    generic_allocator.root()->PurgeMemory(
+        PartitionPurgeDiscardUnusedSystemPages);
     CheckPageInCore(ptr1 - kPointerOffset + (kSystemPageSize * 30), true);
     CheckPageInCore(ptr1 - kPointerOffset + (kSystemPageSize * 31), false);
 
-    PartitionFreeGeneric(generic_allocator.root(), ptr1);
+    generic_allocator.root()->Free(ptr1);
   }
 #else
   {