style: Remove DeclarationPushMode.

Bug: 1473180
Reviewed-by: emilio
MozReview-Commit-ID: LFgYeKE1SNk

components/style/properties/declaration_block.rs

@@ -64,19 +64,6 @@ pub struct SourcePropertyDeclarationUpdate {
     any_removal: bool,
 }
 
-/// Enum for how a given declaration should be pushed into a declaration block.
-#[derive(Clone, Copy, Debug, Eq, Hash, MallocSizeOf, PartialEq)]
-pub enum DeclarationPushMode {
-    /// Mode used when declarations were obtained from CSS parsing.
-    /// If there is an existing declaration of the same property with a higher
-    /// importance, the new declaration will be discarded. Otherwise, it will
-    /// be appended to the end of the declaration block.
-    Parsing,
-    /// In this mode, the new declaration is always pushed to the end of the
-    /// declaration block. This is another possible behavior of CSSOM.
-    Append,
-}
-
 /// A declaration [importance][importance].
 ///
 /// [importance]: https://drafts.csswg.org/css-cascade/#importance
@@ -472,10 +459,7 @@ impl PropertyDeclarationBlock {
         &mut self,
         mut drain: SourcePropertyDeclarationDrain,
         importance: Importance,
-        mode: DeclarationPushMode,
     ) -> bool {
-        match mode {
-            DeclarationPushMode::Parsing => {
         let all_shorthand_len = match drain.all_shorthand {
             AllShorthand::NotSet => 0,
             AllShorthand::CSSWideKeyword(_) |
@@ -486,42 +470,25 @@ impl PropertyDeclarationBlock {
 
         // With deduplication the actual length increase may be less than this.
         self.declarations.reserve(push_calls_count);
-            }
-            _ => {
-                // Don't bother reserving space, since it's usually the case
-                // that CSSOM just overrides properties and we don't need to use
-                // more memory. See bug 1424346 for an example where this
-                // matters.
-                //
-                // TODO: Would it be worth to call reserve() just if it's empty?
-            }
-        }
 
         let mut changed = false;
         for decl in &mut drain.declarations {
-            changed |= self.push(
+            changed |= self.push(decl, importance);
-                decl,
-                importance,
-                mode,
-            );
         }
         drain.all_shorthand.declarations().fold(changed, |changed, decl| {
-            changed | self.push(decl, importance, mode)
+            changed | self.push(decl, importance)
         })
     }
 
     /// Adds or overrides the declaration for a given property in this block.
     ///
-    /// Depending on the value of `mode`, this has a different behavior in the
-    /// presence of another declaration with the same ID in the declaration
-    /// block.
-    ///
     /// Returns whether the declaration has changed.
+    ///
+    /// This is only used for parsing and internal use.
     pub fn push(
         &mut self,
         declaration: PropertyDeclaration,
         importance: Importance,
-        mode: DeclarationPushMode,
     ) -> bool {
         if !self.is_definitely_new(&declaration) {
             let mut index_to_remove = None;
@@ -530,7 +497,6 @@ impl PropertyDeclarationBlock {
                     continue;
                 }
 
-                if matches!(mode, DeclarationPushMode::Parsing) {
                 let important = self.declarations_importance[i];
 
                 // For declarations from parsing, non-important declarations
@@ -554,7 +520,6 @@ impl PropertyDeclarationBlock {
                         }
                     }
                 }
-                }
 
                 index_to_remove = Some(i);
                 break;
@@ -1400,7 +1365,6 @@ pub fn parse_property_declaration_list(
                 block.extend(
                     iter.parser.declarations.drain(),
                     importance,
-                    DeclarationPushMode::Parsing,
                 );
             }
             Err((error, slice)) => {

components/style/stylesheets/keyframes_rule.rs

@@ -8,7 +8,7 @@ use cssparser::{AtRuleParser, CowRcStr, Parser, ParserInput, QualifiedRuleParser
 use cssparser::{parse_one_rule, DeclarationListParser, DeclarationParser, SourceLocation, Token};
 use error_reporting::ContextualParseError;
 use parser::ParserContext;
-use properties::{DeclarationPushMode, Importance, PropertyDeclaration};
+use properties::{Importance, PropertyDeclaration};
 use properties::{LonghandId, PropertyDeclarationBlock, PropertyId};
 use properties::{PropertyDeclarationId, SourcePropertyDeclaration};
 use properties::LonghandIdSet;
@@ -554,7 +554,6 @@ impl<'a, 'i> QualifiedRuleParser<'i> for KeyframeListParser<'a> {
                     block.extend(
                         iter.parser.declarations.drain(),
                         Importance::Normal,
-                        DeclarationPushMode::Parsing,
                     );
                 },
                 Err((error, slice)) => {