DevTools: install resizer on horizontal headers in Sources.

third_party/WebKit/Source/devtools/front_end/sources/SourcesPanel.js

Index: third_party/WebKit/Source/devtools/front_end/sources/SourcesPanel.js
diff --git a/third_party/WebKit/Source/devtools/front_end/sources/SourcesPanel.js b/third_party/WebKit/Source/devtools/front_end/sources/SourcesPanel.js
index 3b9f34577c01cb8e9312496405f25afe10293f2c..c54e0e7f245b1eea991c91172f7d7bd621b782d3 100644
--- a/third_party/WebKit/Source/devtools/front_end/sources/SourcesPanel.js
+++ b/third_party/WebKit/Source/devtools/front_end/sources/SourcesPanel.js
@@ -1045,12 +1045,18 @@ Sources.SourcesPanel = class extends UI.Panel {
     var jsBreakpoints = /** @type {!UI.View} */ (UI.viewManager.view('sources.jsBreakpoints'));
     var scopeChainView = /** @type {!UI.View} */ (UI.viewManager.view('sources.scopeChain'));
 
+    if (this._tabbedLocationHeader) {
+      this._splitWidget.uninstallResizer(this._tabbedLocationHeader);
+      this._tabbedLocationHeader = null;
+    }
+
     if (!vertically) {
       // Populate the rest of the stack.
       this._sidebarPaneStack.showView(scopeChainView);
       this._sidebarPaneStack.showView(jsBreakpoints);
       this._extensionSidebarPanesContainer = this._sidebarPaneStack;
       this.sidebarPaneView = vbox;
+      this._splitWidget.uninstallResizer(this._debugToolbar.element);
     } else {
       var splitWidget = new UI.SplitWidget(true, true, 'sourcesPanelDebuggerSidebarSplitViewState', 0.5);
       splitWidget.setMainWidget(vbox);
@@ -1060,6 +1066,9 @@ Sources.SourcesPanel = class extends UI.Panel {
 
       var tabbedLocation = UI.viewManager.createTabbedLocation(this._revealDebuggerSidebar.bind(this));
       splitWidget.setSidebarWidget(tabbedLocation.tabbedPane());
+      this._tabbedLocationHeader = tabbedLocation.tabbedPane().headerElement();
+      this._splitWidget.installResizer(this._tabbedLocationHeader);
+      this._splitWidget.installResizer(this._debugToolbar.element);

[alph, 2017/05/23 21:23:07]

Is it ok to call this multiple times for _debugToolbar?

       tabbedLocation.appendView(scopeChainView);
       tabbedLocation.appendView(this._watchSidebarPane);
       this._extensionSidebarPanesContainer = tabbedLocation;