repurpose md-fullscreen as md-fill for absolute

src/lib/core/style/_layout-common.scss

@@ -0,0 +1,8 @@
+// This mixin ensures an element spans to fill the nearest ancestor with defined positioning.
+@mixin md-fill {
+  position: absolute;
+  top: 0;
+  left: 0;
+  right: 0;
+  bottom: 0;
+}

src/lib/menu/menu.scss

@@ -2,7 +2,7 @@
 // TODO(kara): animation for menu opening
 
 @import '../core/style/button-common';
-@import '../core/style/sidenav-common';
+@import '../core/style/layout-common';
 @import '../core/style/menu-common';
 
 $md-menu-vertical-padding: 8px !default;

src/lib/sidenav/sidenav.scss

@@ -1,6 +1,6 @@
 @import '../core/style/variables';
 @import '../core/style/elevation';
-@import '../core/style/sidenav-common';
+@import '../core/style/layout-common';
 
 
 // Mixin to help with defining LTR/RTL 'transform: translate3d()' values.
@@ -57,7 +57,7 @@ md-sidenav-layout {
 
   // TODO(hansl): Update this with a more robust solution.
   &[fullscreen] {
-    @include md-fullscreen();
+    @include md-fill();
 
     &.md-sidenav-opened {
       overflow: hidden;
@@ -66,7 +66,7 @@ md-sidenav-layout {
 }
 
 .md-sidenav-backdrop {
-  @include md-fullscreen();
+  @include md-fill();
 
   display: block;
 

src/lib/tabs/tab-group.scss

@@ -1,4 +1,5 @@
 @import '../core/style/variables';
+@import '../core/style/layout-common';
 @import 'tabs-common';
 
 :host {
@@ -38,12 +39,8 @@ md-ink-bar {
 
 // Wraps each tab body 
 md-tab-body {
+  @include md-fill;
   display: block;
-  position: absolute;
-  top: 0;
-  right: 0;
-  bottom: 0;
-  left: 0;
   overflow: hidden;
   &.md-tab-body-active {
     position: relative;