Set the constant pool size to 0 on architectures that do not use it.

Turns out we've been putting garbage into code->constant_pool_offset
for quite some time.

R=jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1478713002

Cr-Commit-Position: refs/heads/master@{#32269}

src/arm64/assembler-arm64.cc

@@ -589,6 +589,7 @@ void Assembler::GetCode(CodeDesc* desc) {
         static_cast<int>((reinterpret_cast<byte*>(buffer_) + buffer_size_) -
                          reloc_info_writer.pos());
     desc->origin = this;
+    desc->constant_pool_size = 0;
   }
 }
 

src/ia32/assembler-ia32.cc

@@ -338,6 +338,7 @@ void Assembler::GetCode(CodeDesc* desc) {
   desc->instr_size = pc_offset();
   desc->reloc_size = (buffer_ + buffer_size_) - reloc_info_writer.pos();
   desc->origin = this;
+  desc->constant_pool_size = 0;
 }
 
 

src/mips/assembler-mips.cc

@@ -296,6 +296,7 @@ void Assembler::GetCode(CodeDesc* desc) {
   desc->instr_size = pc_offset();
   desc->reloc_size = (buffer_ + buffer_size_) - reloc_info_writer.pos();
   desc->origin = this;
+  desc->constant_pool_size = 0;
 }
 
 

src/mips64/assembler-mips64.cc

@@ -272,6 +272,7 @@ void Assembler::GetCode(CodeDesc* desc) {
   desc->reloc_size =
       static_cast<int>((buffer_ + buffer_size_) - reloc_info_writer.pos());
   desc->origin = this;
+  desc->constant_pool_size = 0;
 }
 
 

src/x64/assembler-x64.cc

@@ -292,6 +292,7 @@ void Assembler::GetCode(CodeDesc* desc) {
   desc->reloc_size =
       static_cast<int>((buffer_ + buffer_size_) - reloc_info_writer.pos());
   desc->origin = this;
+  desc->constant_pool_size = 0;
 }
 
 

src/x87/assembler-x87.cc

@@ -253,6 +253,7 @@ void Assembler::GetCode(CodeDesc* desc) {
   desc->instr_size = pc_offset();
   desc->reloc_size = (buffer_ + buffer_size_) - reloc_info_writer.pos();
   desc->origin = this;
+  desc->constant_pool_size = 0;
 }