Make base::WeakPtr::Get() fast

base/memory/weak_ptr_unittest.nc

Index: base/memory/weak_ptr_unittest.nc
diff --git a/base/memory/weak_ptr_unittest.nc b/base/memory/weak_ptr_unittest.nc
index 9b1226b7941da4117732b211dffe490e9caf9017..d86b0efe5156023129121a438052aaf31e8b6296 100644
--- a/base/memory/weak_ptr_unittest.nc
+++ b/base/memory/weak_ptr_unittest.nc
@@ -17,7 +17,7 @@ struct MultiplyDerivedProducer : Producer,
 struct Unrelated {};
 struct DerivedUnrelated : Unrelated {};
 
-#if defined(NCTEST_AUTO_DOWNCAST)  // [r"fatal error: cannot initialize a member subobject of type 'base::DerivedProducer \*' with an lvalue of type 'base::Producer \*const'"]
+#if defined(NCTEST_AUTO_DOWNCAST)  // [r'fatal error: static_assert failed "other must be a subclass of T"']

[Nico, 2017/06/28 14:36:56]

The changes in this CL also feel like they could be in a different CL (plus the
static_asserts in the header)

[hans, 2017/06/28 20:37:35]

Yeah, this is part of the "move ptr_ into WeakPtrBase" change; splitting that
out.

 
 void WontCompile() {
   Producer f;
@@ -25,7 +25,7 @@ void WontCompile() {
   WeakPtr<DerivedProducer> derived_ptr = ptr;
 }
 
-#elif defined(NCTEST_STATIC_DOWNCAST)  // [r"fatal error: cannot initialize a member subobject of type 'base::DerivedProducer \*' with an lvalue of type 'base::Producer \*const'"]
+#elif defined(NCTEST_STATIC_DOWNCAST)  // [r'fatal error: static_assert failed "other must be a subclass of T"']
 
 void WontCompile() {
   Producer f;
@@ -59,7 +59,7 @@ void WontCompile() {
       SupportsWeakPtr<Producer>::StaticAsWeakPtr<DerivedProducer>(&f);
 }
 
-#elif defined(NCTEST_UNSAFE_HELPER_DOWNCAST)  // [r"fatal error: cannot initialize a member subobject of type 'base::DerivedProducer \*' with an lvalue of type 'base::Producer \*'"]
+#elif defined(NCTEST_UNSAFE_HELPER_DOWNCAST)  // [r'fatal error: static_assert failed "other must be a subclass of T"']
 
 void WontCompile() {
   Producer f;
@@ -73,14 +73,14 @@ void WontCompile() {
   WeakPtr<DerivedProducer> ptr = AsWeakPtr<DerivedProducer>(&f);
 }
 
-#elif defined(NCTEST_UNSAFE_WRONG_INSANTIATED_HELPER_DOWNCAST)  // [r"fatal error: cannot initialize a member subobject of type 'base::DerivedProducer \*' with an lvalue of type 'base::Producer \*'"]
+#elif defined(NCTEST_UNSAFE_WRONG_INSANTIATED_HELPER_DOWNCAST)  // [r'fatal error: static_assert failed "other must be a subclass of T"']
 
 void WontCompile() {
-  Producer f; 
+  Producer f;
   WeakPtr<DerivedProducer> ptr = AsWeakPtr<Producer>(&f);
 }
 
-#elif defined(NCTEST_UNSAFE_HELPER_CAST)  // [r"fatal error: cannot initialize a member subobject of type 'base::OtherDerivedProducer \*' with an lvalue of type 'base::DerivedProducer \*'"]
+#elif defined(NCTEST_UNSAFE_HELPER_CAST)  // [r'fatal error: static_assert failed "other must be a subclass of T"']
 
 void WontCompile() {
   DerivedProducer f;
@@ -94,14 +94,14 @@ void WontCompile() {
   WeakPtr<OtherDerivedProducer> ptr = AsWeakPtr<OtherDerivedProducer>(&f);
 }
 
-#elif defined(NCTEST_UNSAFE_WRONG_INSTANTIATED_HELPER_SIDECAST)  // [r"fatal error: cannot initialize a member subobject of type 'base::OtherDerivedProducer \*' with an lvalue of type 'base::DerivedProducer \*'"]
+#elif defined(NCTEST_UNSAFE_WRONG_INSTANTIATED_HELPER_SIDECAST)  // [r'fatal error: static_assert failed "other must be a subclass of T"']
 
 void WontCompile() {
   DerivedProducer f;
   WeakPtr<OtherDerivedProducer> ptr = AsWeakPtr<DerivedProducer>(&f);
 }
 
-#elif defined(NCTEST_UNRELATED_HELPER)  // [r"fatal error: cannot initialize a member subobject of type 'base::Unrelated \*' with an lvalue of type 'base::DerivedProducer \*'"]
+#elif defined(NCTEST_UNRELATED_HELPER)  // [r'fatal error: static_assert failed "other must be a subclass of T"']
 
 void WontCompile() {
   DerivedProducer f;