ART: PathClassLoader for compiler

Use an actual PathClassLoader when compiling apps, instead of a
side structure and cutout.

This CL sets up a minimal object 'cluster' that recreates the Java
side of a regular ClassLoader such that the Class-Linker will
recognize it and use the internal native fast-path.

This CL removes the now unnecessary compile-time-classpath and
replaces it with a single 'compiling-the-boot-image' flag in the
compiler callbacks.

Note: This functionality is *only* intended for the compiler, as
the objects have not been completely initialized.

Bug: 19781184

Change-Id: I7f36af12dd7852d21281110a25c119e8c0669c1d
diff --git a/compiler/jit/jit_compiler.cc b/compiler/jit/jit_compiler.cc
index 8b31154..d034736 100644
--- a/compiler/jit/jit_compiler.cc
+++ b/compiler/jit/jit_compiler.cc
@@ -89,7 +89,8 @@
   verification_results_.reset(new VerificationResults(compiler_options_.get()));
   method_inliner_map_.reset(new DexFileToMethodInlinerMap);
   callbacks_.reset(new QuickCompilerCallbacks(verification_results_.get(),
-                                              method_inliner_map_.get()));
+                                              method_inliner_map_.get(),
+                                              false));
   compiler_driver_.reset(new CompilerDriver(
       compiler_options_.get(), verification_results_.get(), method_inliner_map_.get(),
       Compiler::kQuick, instruction_set, instruction_set_features_.get(), false,