Tabs & Dropdown: fix style (#14452)

packages/theme-chalk/src/dropdown.scss

@@ -69,6 +69,8 @@
   border: 1px solid $--border-color-lighter;
   border-radius: $--border-radius-base;
   box-shadow: $--dropdown-menu-box-shadow;
+  max-height: 400px;
+  overflow: auto;
 
   @include e(item) {
     list-style: none;

packages/theme-chalk/src/tabs.scss

@@ -211,10 +211,10 @@
     border: 1px solid $--border-color-base;
     box-shadow: 0 2px 4px 0 rgba(0,0,0,0.12), 0 0 6px 0 rgba(0,0,0,0.04);
 
-    >.el-tabs__content {
+    > .el-tabs__content {
       padding: 15px;
     }
-    >.el-tabs__header {
+    > .el-tabs__header {
       background-color: $--background-color-base;
       border-bottom: 1px solid $--border-color-light;
       margin: 0;
@@ -222,12 +222,20 @@
     > .el-tabs__header .el-tabs__nav-wrap::after {
       content: none;
     }
-    >.el-tabs__header .el-tabs__item {
+    > .el-tabs__header .el-tabs__item {
       transition: all .3s cubic-bezier(.645,.045,.355,1);
       border: 1px solid transparent;
-      margin: -1px -1px 0;
+      margin-top: -1px;
       color: $--color-text-secondary;
 
+      &:first-child {
+        margin-left: -1px;
+      }
+
+      & + .el-tabs__item {
+        margin-left: -1px;
+      }
+
       &.is-active {
         color: $--color-primary;
         background-color: $--color-white;
@@ -241,6 +249,10 @@
         color: $--disabled-color-base;
       }
     }
+
+    > .el-tabs__header .is-scrollable .el-tabs__item:first-child {
+      margin-left: 0;
+    }
   }
   @include m((top, bottom)) {
     .el-tabs__item.is-top:nth-child(2),