Add compiling class to the DexCompilationUnit.

Use it to simplify HInstructionBuilder and reduce the
number of class resolution calls.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Test: Pixel 2 XL boots.
Change-Id: Ib4f9b4ea61235841e653a03a40755a39c7de7504
diff --git a/compiler/driver/dex_compilation_unit.h b/compiler/driver/dex_compilation_unit.h
index c1ae3c9..9d9c218 100644
--- a/compiler/driver/dex_compilation_unit.h
+++ b/compiler/driver/dex_compilation_unit.h
@@ -27,6 +27,7 @@
 
 namespace art {
 namespace mirror {
+class Class;
 class ClassLoader;
 class DexCache;
 }  // namespace mirror
@@ -43,7 +44,8 @@
                      uint32_t method_idx,
                      uint32_t access_flags,
                      const VerifiedMethod* verified_method,
-                     Handle<mirror::DexCache> dex_cache);
+                     Handle<mirror::DexCache> dex_cache,
+                     Handle<mirror::Class> compiling_class = Handle<mirror::Class>());
 
   Handle<mirror::ClassLoader> GetClassLoader() const {
     return class_loader_;
@@ -117,6 +119,10 @@
     return code_item_accessor_;
   }
 
+  Handle<mirror::Class> GetCompilingClass() const {
+    return compiling_class_;
+  }
+
  private:
   const Handle<mirror::ClassLoader> class_loader_;
 
@@ -134,6 +140,8 @@
 
   const CodeItemDataAccessor code_item_accessor_;
 
+  Handle<mirror::Class> compiling_class_;
+
   std::string symbol_;
 };