Merge branch 'revert-diff-scroll' into 'master'

Wrap all code in diffs

Closes #15382  
Closes #15422  
All diff code wraps to next line instead of scrolling

<img src="/uploads/ec5754919bac0b027fcb122bb88435b3/Screen_Shot_2016-04-20_at_12.22.27_PM.png" width="500px">

See merge request !3838

app/assets/stylesheets/framework/markdown_area.scss

@@ -90,3 +90,12 @@
   box-shadow: none;
   width: 100%;
 }
+
+.md {
+  &.md-preview-holder {
+    code {
+      white-space: pre-wrap;
+      word-break: break-all;
+    }
+  }
+}

app/assets/stylesheets/pages/detail_page.scss

@@ -36,4 +36,10 @@
       }
     }
   }
+
+  .wiki {
+    code {
+      white-space: pre-wrap;
+    }
+  }
 }

app/assets/stylesheets/pages/diff.scss

@@ -87,7 +87,7 @@
         }
 
         span {
-          white-space: pre;
+          white-space: pre-wrap;
         }
       }
     }
@@ -336,7 +336,7 @@
 }
 
 .diff-file .line_content {
-  white-space: pre;
+  white-space: pre-wrap;
 }
 
 .diff-wrap-lines .line_content {

app/assets/stylesheets/pages/note_form.scss

@@ -84,18 +84,6 @@
         border-color: $gl-success;
       }
     }
-
-    p {
-      code {
-        white-space: normal;
-      }
-
-      pre {
-        code {
-          white-space: pre;
-        }
-      }
-    }
   }
 }
 

app/assets/stylesheets/pages/notes.scss

@@ -81,16 +81,8 @@ ul.notes {
         @include md-typography;
 
         // On diffs code should wrap nicely and not overflow
-        p {
         code {
-            white-space: normal;
-          }
-
-          pre {
-            code {
-              white-space: pre;
-            }
-          }
+          white-space: pre-wrap;
         }
 
         // Reset ul style types since we're nested inside a ul already
@@ -137,7 +129,7 @@ ul.notes {
     margin-right: 10px;
   }
   .line_content {
-    white-space: pre;
+    white-space: pre-wrap;
   }
 }
 
@@ -171,11 +163,6 @@ ul.notes {
 
       &.parallel {
         border-width: 1px;
-
-        .code,
-        code {
-          white-space: pre-wrap;
-        }
       }
 
       .notes {