Add use-chromium-style-naming option to Blink GC plugin.

tools/clang/blink_gc_plugin/tests/legacy_naming/stack_allocated.txt

+In file included from stack_allocated.cpp:5:
+./stack_allocated.h:14:1: warning: [blink-gc] Class 'PartObject' requires a trace method.
+class PartObject {
+^
+./stack_allocated.h:17:5: note: [blink-gc] Untraced field 'm_obj' declared here:
+    Member<HeapObject> m_obj; // Needs tracing.
+    ^
+./stack_allocated.h:26:1: warning: [blink-gc] Class 'HeapObject' contains invalid fields.
+class HeapObject : public GarbageCollected<HeapObject> {
+^
+./stack_allocated.h:30:5: note: [blink-gc] Stack-allocated field 'm_part' declared here:
+    StackObject m_part; // Cannot embed a stack allocated object.
+    ^
+./stack_allocated.h:34:27: warning: [blink-gc] Stack-allocated class 'DerivedHeapObject' derives class 'HeapObject' which is garbage collected.
+class DerivedHeapObject : public HeapObject, public StackObject {
+                          ^
+./stack_allocated.h:38:28: warning: [blink-gc] Stack-allocated class 'DerivedHeapObject2' derives class 'HeapObject' which is garbage collected.
+class DerivedHeapObject2 : public HeapObject {
+                           ^
+./stack_allocated.h:39:3: warning: [blink-gc] Garbage collected class 'DerivedHeapObject2' is not permitted to override its new operator.
+  STACK_ALLOCATED();
+  ^
+./heap/stubs.h:149:5: note: expanded from macro 'STACK_ALLOCATED'
+    __attribute__((annotate("blink_stack_allocated")))      \
+    ^
+stack_allocated.cpp:12:1: warning: [blink-gc] Class 'AnonStackObject' contains invalid fields.
+class AnonStackObject : public StackObject {
+^
+stack_allocated.cpp:14:5: note: [blink-gc] Raw pointer field 'm_obj' to a GC managed class declared here:
+    HeapObject* m_obj;
+    ^
+6 warnings generated.