Support locking of directory entries

Moves the locking algorithm from file entry to file system entry.

Fixes whatwg#137

Author: Nathan Memmott

index.bs

@@ -130,13 +130,13 @@ result of [=starting a new parallel queue=]. This queue is to be used for all
 file sytem operations.
 
 <div algorithm>
-To <dfn for="file system entry/lock">take</dfn> a [=file system entry/lock=] with a |value| of
+To <dfn for="file system entry/lock">take a lock</dfn> with a |value| of
 "`exclusive`" or "`shared`" on a given [=/file system entry=] |entry|:
 
 1. Let |lock| be the |entry|'s [=file system entry/lock=].
 1. Let |count| be the |entry|'s [=file system entry/shared lock count=].
-1. Let |hasDescendantLock| be the result of [=file system entry/lock/checking for a descendant lock=] on |entry|.
-1. If |hasDescendantLock| is true:
+1. Let |descendantLockStatus| be the result of [=file system entry/lock/checking for a descendant lock=] on |entry|.
+1. If |descendantLockStatus| is "`taken`":
    1. Return "`failure`".
 1. If |value| is "`exclusive`":
    1. If |lock| is "`open`":
@@ -162,13 +162,13 @@ To <dfn for="file system entry/lock">check for a descendant lock</dfn> on a give
 
 1. Let |lock| be the |entry|'s [=file system entry/lock=].
 1. If |lock| is not "`open`":
-   1. Return true.
+   1. Return "`taken`".
 1. If |entry| is a [=directory entry=]:
    1. [=set/For each=] |child| of |entry|'s [=directory entry/children=]:
-      1. Let |hasDescendantLock| be the result of [=file system entry/lock/checking for a descendant lock=] on |child|.
-      1. If |hasDescendantLock| is true:
-         1. Return true.
-1. Return false.
+      1. Let |descendantLockStatus| be the result of [=file system entry/lock/checking for a descendant lock=] on |child|.
+      1. If |descendantLockStatus| is "`taken`":
+         1. Return "`taken`".
+1. Return "`open`".
 
 Note: These steps have to be run on the [=file system queue=].
 
@@ -558,7 +558,7 @@ The <dfn method for=FileSystemFileHandle>getFile()</dfn> method steps are:
      the temporary file starts out empty,
      otherwise the existing file is first copied to this temporary file.
 
-     Creating a {{FileSystemWritableFileStream}} [=file system entry/lock/take|takes a shared lock=] on the
+     Creating a {{FileSystemWritableFileStream}} [=file system entry/lock/take a lock|takes a shared lock=] on the
      [=file entry=] [=locate an entry|locatable=] with |fileHandle|'s [=FileSystemHandle/locator=].
      This prevents the creation of {{FileSystemSyncAccessHandle|FileSystemSyncAccessHandles}}
      for the entry, until the stream is closed.
@@ -595,7 +595,7 @@ The <dfn method for=FileSystemFileHandle>createWritable(|options|)</dfn> method
      |result| with a "{{NotFoundError}}" {{DOMException}} and abort these steps.
   1. [=Assert=]: |entry| is a [=file entry=].
 
-  1. Let |lockResult| be the result of [=file system entry/lock/take|taking a lock=]
+  1. Let |lockResult| be the result of [=file system entry/lock/take a lock|taking a lock=]
      with "`shared`" on |entry|.
 
   1. [=Queue a storage task=] with |global| to run these steps:
@@ -623,7 +623,7 @@ The <dfn method for=FileSystemFileHandle>createWritable(|options|)</dfn> method
      [=file entry=] [=locate an entry|locatable=] by |fileHandle|'s [=FileSystemHandle/locator=].
      To ensure the changes are reflected in this file, the handle can be flushed.
 
-     Creating a {{FileSystemSyncAccessHandle}} [=file system entry/lock/take|takes an exclusive lock=] on the
+     Creating a {{FileSystemSyncAccessHandle}} [=file system entry/lock/take a lock|takes an exclusive lock=] on the
      [=file entry=] [=locate an entry|locatable=] with |fileHandle|'s [=FileSystemHandle/locator=].
      This prevents the creation of further {{FileSystemSyncAccessHandle|FileSystemSyncAccessHandles}}
      or {{FileSystemWritableFileStream|FileSystemWritableFileStreams}}
@@ -665,7 +665,7 @@ The <dfn method for=FileSystemFileHandle>createSyncAccessHandle()</dfn> method s
      |result| with a "{{NotFoundError}}" {{DOMException}} and abort these steps.
   1. [=Assert=]: |entry| is a [=file entry=].
 
-  1. Let |lockResult| be the result of [=file system entry/lock/take|taking a lock=]
+  1. Let |lockResult| be the result of [=file system entry/lock/take a lock|taking a lock=]
      with "`exclusive`" on |entry|.
 
   1. [=Queue a storage task=] with |global| to run these steps: