Make base::WeakPtr move constructor/operator noexcept to fix GCC build regression

A GCC build regression has happened on DisjointRangeLockManager, as its move
operator and constructor were declared noexcept. This was failing because the
default implementation depended on base::WeakPtr, that did not provide
noexcept declaration for them.

So make base::WeakPtr noexcept.

Bug: 819294
Change-Id: I936784b881c7c1afea136ceedbe9341e76464f95
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1708141Reviewed-by: Victor Costan <pwnall@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: José Dapena Paz <jose.dapena@lge.com>
Cr-Commit-Position: refs/heads/master@{#680341}

base/memory/weak_ptr.cc

@@ -46,7 +46,7 @@ WeakReference::WeakReference(const scoped_refptr<Flag>& flag) : flag_(flag) {}
 
 WeakReference::~WeakReference() = default;
 
-WeakReference::WeakReference(WeakReference&& other) = default;
+WeakReference::WeakReference(WeakReference&& other) noexcept = default;
 
 WeakReference::WeakReference(const WeakReference& other) = default;
 

base/memory/weak_ptr.h

@@ -116,9 +116,9 @@ class BASE_EXPORT WeakReference {
   explicit WeakReference(const scoped_refptr<Flag>& flag);
   ~WeakReference();
 
-  WeakReference(WeakReference&& other);
+  WeakReference(WeakReference&& other) noexcept;
   WeakReference(const WeakReference& other);
-  WeakReference& operator=(WeakReference&& other) = default;
+  WeakReference& operator=(WeakReference&& other) noexcept = default;
   WeakReference& operator=(const WeakReference& other) = default;
 
   bool IsValid() const;
@@ -153,9 +153,9 @@ class BASE_EXPORT WeakPtrBase {
   ~WeakPtrBase();
 
   WeakPtrBase(const WeakPtrBase& other) = default;
-  WeakPtrBase(WeakPtrBase&& other) = default;
+  WeakPtrBase(WeakPtrBase&& other) noexcept = default;
   WeakPtrBase& operator=(const WeakPtrBase& other) = default;
-  WeakPtrBase& operator=(WeakPtrBase&& other) = default;
+  WeakPtrBase& operator=(WeakPtrBase&& other) noexcept = default;
 
   void reset() {
     ref_ = internal::WeakReference();
@@ -236,7 +236,7 @@ class WeakPtr : public internal::WeakPtrBase {
     ptr_ = reinterpret_cast<uintptr_t>(t);
   }
   template <typename U>
-  WeakPtr(WeakPtr<U>&& other) : WeakPtrBase(std::move(other)) {
+  WeakPtr(WeakPtr<U>&& other) noexcept : WeakPtrBase(std::move(other)) {
     // Need to cast from U* to T* to do pointer adjustment in case of multiple
     // inheritance. This also enforces the "U is a T" rule.
     T* t = reinterpret_cast<U*>(other.ptr_);