Clean up frontend.h includes and forward declarations.

Remove unused and add needed includes and forward
declarations. Explicitly include "invoke_type.h" instead
of relying on indirect inclusion via "dex_file.h".

Change-Id: Ic7a2e0e9a1f29f10008ca42a1183e357d132fd88
diff --git a/compiler/dex/frontend.h b/compiler/dex/frontend.h
index 8eb6684..8ce1206 100644
--- a/compiler/dex/frontend.h
+++ b/compiler/dex/frontend.h
@@ -18,12 +18,7 @@
 #define ART_COMPILER_DEX_FRONTEND_H_
 
 #include "dex_file.h"
-#include "dex_instruction.h"
-
-
-
-
-
+#include "invoke_type.h"
 
 namespace llvm {
   class Module;
@@ -82,9 +77,6 @@
   kDebugTimings
 };
 
-class DexFileToMethodInlinerMap;
-class CompilerDriver;
-
 class LLVMInfo {
   public:
     LLVMInfo();
@@ -113,8 +105,8 @@
     UniquePtr<art::llvm::IRBuilder> ir_builder_;
 };
 
-struct CompilationUnit;
-struct BasicBlock;
+struct CompiledMethod;
+class CompilerDriver;
 
 }  // namespace art