Fix AssemblerMIPS64Test.LongBalc() running out of memory.

Pre-allocate the necessary buffer because the reallocation
strategy doesn't work well for a test of this size.

Test: m test-art-host-gtest-assembler_mips64_test
Change-Id: I16bc75f0ae83a62e5f3ed2cd8228dd40f0eb9524
diff --git a/compiler/utils/mips64/assembler_mips64_test.cc b/compiler/utils/mips64/assembler_mips64_test.cc
index 31d3e4c..f62822d 100644
--- a/compiler/utils/mips64/assembler_mips64_test.cc
+++ b/compiler/utils/mips64/assembler_mips64_test.cc
@@ -605,15 +605,18 @@
 }
 
 TEST_F(AssemblerMIPS64Test, LongBalc) {
+  constexpr uint32_t kNopCount1 = (1u << 25) + 1;
+  constexpr uint32_t kNopCount2 = (1u << 25) + 1;
+  constexpr uint32_t kRequiredCapacity = (kNopCount1 + kNopCount2 + 6u) * 4u;
+  ASSERT_LT(__ GetBuffer()->Capacity(), kRequiredCapacity);
+  __ GetBuffer()->ExtendCapacity(kRequiredCapacity);
   mips64::Mips64Label label1, label2;
   __ Balc(&label1);
-  constexpr uint32_t kNopCount1 = (1u << 25) + 1;
   for (uint32_t i = 0; i != kNopCount1; ++i) {
     __ Nop();
   }
   __ Bind(&label1);
   __ Balc(&label2);
-  constexpr uint32_t kNopCount2 = (1u << 25) + 1;
   for (uint32_t i = 0; i != kNopCount2; ++i) {
     __ Nop();
   }