Make java_sdk_library implement Dependency

dexpreopting boot jars is going to need to visit both java_library
and java_sdk_library modules.  Since java_sdk_library is already
a java_library module, move the SdkLibraryDependency methods out
of the way so that it will implement Dependency.  Also requries
re-ording some of the type switches to check for the more-specific
SdkLibraryDependency first.

Test: TestJavaSdkLibrary
Change-Id: I155c9ffaf31689dd150a4d99e07e432ff770b4a7

java/droiddoc.go

@@ -630,10 +630,10 @@ func (j *Javadoc) collectDeps(ctx android.ModuleContext) deps {
 			}
 		case libTag:
 			switch dep := module.(type) {
+			case SdkLibraryDependency:
+				deps.classpath = append(deps.classpath, dep.SdkImplementationJars(ctx, j.sdkVersion())...)
 			case Dependency:
 				deps.classpath = append(deps.classpath, dep.HeaderJars()...)
-			case SdkLibraryDependency:
-				deps.classpath = append(deps.classpath, dep.ImplementationJars(ctx, j.sdkVersion())...)
 			case android.SourceFileProducer:
 				checkProducesJars(ctx, dep)
 				deps.classpath = append(deps.classpath, dep.Srcs()...)