DevTools: fix style of blackbox list and workspace labels

Screenshot: https://imgur.com/a/d5iLM

Bug: 771931
Change-Id: I8b3abd912cedfcc74f9deff87c9e5885cfc26678
Reviewed-on: https://chromium-review.googlesource.com/777841Reviewed-by: Andrey Lushnikov <lushnikov@chromium.org>
Commit-Queue: Erik Luo <luoe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#519883}

third_party/WebKit/Source/devtools/front_end/persistence/editFileSystemView.css

@@ -13,7 +13,7 @@
 }
 
 .file-system-header-text {
-    flex: auto;
+    flex: 1 0 auto;
 }
 
 .add-button {

third_party/WebKit/Source/devtools/front_end/settings/frameworkBlackboxSettingsTab.css

@@ -61,6 +61,7 @@
 
 .blackbox-pattern {
     flex: auto;
+    min-width: 100px;
 }
 
 .blackbox-list-item.blackbox-disabled .blackbox-pattern {

third_party/WebKit/Source/devtools/front_end/settings/settingsScreen.css

@@ -113,6 +113,7 @@ fieldset {
 .settings-tab label {
     padding-right: 4px;
     display: inline-flex;
+    flex-shrink: 0;
 }
 
 #general-tab-content .help-block fieldset legend {

third_party/WebKit/Source/devtools/front_end/ui/listWidget.css

@@ -22,6 +22,7 @@
     display: flex;
     align-items: center;
     position: relative;
+    overflow: hidden;
 }
 
 .list-item:hover {