Prepare for release 2.59.0 (#9846)

flutter-candidate.txt

diff --git a/flutter-candidate.txt b/flutter-candidate.txt
index 2865847..bf6bf2c 100644
--- a/flutter-candidate.txt
+++ b/flutter-candidate.txt
@@ -1 +1 @@
-f3a4b989783497d9c904b7f0363886248c9175e4
+3648ed5372a7baa2941539b457a3c804ca0afd86

packages/devtools_app/lib/devtools.dart

diff --git a/packages/devtools_app/lib/devtools.dart b/packages/devtools_app/lib/devtools.dart
index 73b0743..511c2a6 100644
--- a/packages/devtools_app/lib/devtools.dart
+++ b/packages/devtools_app/lib/devtools.dart
@@ -10,4 +10,4 @@
 /// Note: a regexp in the `dt update-version' command logic matches the constant
 /// declaration `const version =`. If you change the declaration you must also
 /// modify the regex in the `dt update-version' command logic.
-const version = '2.59.0-dev.0';
+const version = '2.59.0';

packages/devtools_app/pubspec.yaml

diff --git a/packages/devtools_app/pubspec.yaml b/packages/devtools_app/pubspec.yaml
index a0985fa..7d801e1 100644
--- a/packages/devtools_app/pubspec.yaml
+++ b/packages/devtools_app/pubspec.yaml
@@ -7,7 +7,7 @@
 
 # Note: this version should only be updated by running the 'dt update-version'
 # command that updates the version here and in 'devtools.dart'.
-version: 2.59.0-dev.0
+version: 2.59.0
 
 repository: https://github.com/flutter/devtools/tree/master/packages/devtools_app