Prepare to publish analyzer 0.39.15.

Change-Id: Ie7439fa98cd6d9b4b1e5ffb5ff81a16e8ddaf97b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/155832
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

Author: scheglov

pkg/analyzer/CHANGELOG.md

@@ -1,8 +1,10 @@
-## 0.39.15-dev
+## 0.39.15
 * Move `asInstanceOf(ClassElement)` to `DartType`, so that it is also
   supported for `TypeParameterType` when its bound implements the
   requested interface.
 * Fixed invalid implicit downcast in `InterfaceType.allSupertypes`.
+* The internal `currentVersion` of the language updated to `2.10`.
+* Bug fixes: 41065, 42797, 42770, 42668.
 
 ## 0.39.14
 * Removed `defaultSdkDirectory()` and `getSdkProperty()` from internal

pkg/analyzer/pubspec.yaml

@@ -1,5 +1,5 @@
 name: analyzer
-version: 0.39.15-dev
+version: 0.39.15
 description: This package provides a library that performs static analysis of Dart code.
 homepage: https://github.com/dart-lang/sdk/tree/master/pkg/analyzer