Revert of cc: Remove use of PassAs() and constructor-casting with scoped_ptr. (patchset #6 id:120001 of https://codereview.chromium.org/609663003/)

Reason for revert:
scoped_ptr nullptr support needs to be reverted

Original issue's description:
> cc: Remove use of PassAs() and constructor-casting with scoped_ptr.
>
> Say you have class A and subclass B.
>
> Previously it was required to PassAs() a scoped_ptr<B> into a
> scoped_ptr<A>. This is no longer needed, so just use Pass(). For newly
> created scoped_ptrs, you can just use make_scoped_ptr always now.
>
> And when you want to return or assign an empty scoped_ptr(), you can
> now use nullptr directly.
>
> Also adds PRESUBMIT checks for:
> - return scoped<T>(foo). This should be return make_scoped_ptr(foo).
> - bar = scoped<T>(foo). This should be return bar = make_scoped_ptr(foo).
> - return scoped<T>(). This should be return nullptr.
> - bar = scoped<T>(). This should be return bar = nullptr.
>
> This also replaces p.reset() with p = nullptr; But it does not add a
> PRESUBMIT check for that because there are things other than scoped_ptr
> with a reset() function.
>
> R=enne@chromium.org
>
> Committed: https://crrev.com/7bb3dbede19d87f0338797756ffd738adc6bca08
> Cr-Commit-Position: refs/heads/master@{#297096}

TBR=enne@chromium.org,jamesr@chromium.org,vmpstr@chromium.org,danakj@chromium.org
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/608503005

Cr-Commit-Position: refs/heads/master@{#297106}

3 files changed, 6 insertions, 6 deletions

diff --git a/cc/base/math_util.cc b/cc/base/math_util.cc
index 7ed0c9a..5b01da9 100644
--- a/cc/base/math_util.cc
+++ b/cc/base/math_util.cc
@@ -693,7 +693,7 @@ scoped_ptr<base::Value> MathUtil::AsValue(const gfx::Size& s) {
   scoped_ptr<base::DictionaryValue> res(new base::DictionaryValue());
   res->SetDouble("width", s.width());
   res->SetDouble("height", s.height());
-  return res.Pass();
+  return res.PassAs<base::Value>();
 }
 
 scoped_ptr<base::Value> MathUtil::AsValue(const gfx::Rect& r) {
@@ -702,7 +702,7 @@ scoped_ptr<base::Value> MathUtil::AsValue(const gfx::Rect& r) {
   res->AppendInteger(r.y());
   res->AppendInteger(r.width());
   res->AppendInteger(r.height());
-  return res.Pass();
+  return res.PassAs<base::Value>();
 }
 
 bool MathUtil::FromValue(const base::Value* raw_value, gfx::Rect* out_rect) {
@@ -730,7 +730,7 @@ scoped_ptr<base::Value> MathUtil::AsValue(const gfx::PointF& pt) {
   scoped_ptr<base::ListValue> res(new base::ListValue());
   res->AppendDouble(pt.x());
   res->AppendDouble(pt.y());
-  return res.Pass();
+  return res.PassAs<base::Value>();
 }
 
 void MathUtil::AddToTracedValue(const gfx::Size& s,
diff --git a/cc/base/region.cc b/cc/base/region.cc
index d752b20..2484cc2 100644
--- a/cc/base/region.cc
+++ b/cc/base/region.cc
@@ -127,7 +127,7 @@ scoped_ptr<base::Value> Region::AsValue() const {
     result->AppendInteger(rect.width());
     result->AppendInteger(rect.height());
   }
-  return result.Pass();
+  return result.PassAs<base::Value>();
 }
 
 void Region::AsValueInto(base::debug::TracedValue* result) const {
diff --git a/cc/base/scoped_ptr_vector.h b/cc/base/scoped_ptr_vector.h
index 0b83e35..7f86ce3 100644
--- a/cc/base/scoped_ptr_vector.h
+++ b/cc/base/scoped_ptr_vector.h
@@ -72,7 +72,7 @@ class ScopedPtrVector {
 
   scoped_ptr<T> take(iterator position) {
     if (position == end())
-      return nullptr;
+      return scoped_ptr<T>();
     DCHECK(position < end());
 
     typename std::vector<T*>::iterator writable_position = position;
@@ -84,7 +84,7 @@ class ScopedPtrVector {
   scoped_ptr<T> take_back() {
     DCHECK(!empty());
     if (empty())
-      return nullptr;
+      return scoped_ptr<T>(NULL);
     return take(end() - 1);
   }