--- a/accessible/generic/Accessible.h
+++ b/accessible/generic/Accessible.h
@@ -1175,17 +1175,17 @@ private:
  * This class makes sure required tasks are done before and after tree
  * mutations. Currently this only includes group info invalidation. You must
  * have an object of this class on the stack when calling methods that mutate
  * the accessible tree.
  */
 class AutoTreeMutation
 {
 public:
-  AutoTreeMutation(Accessible* aRoot, bool aInvalidationRequired = true) :
+  explicit AutoTreeMutation(Accessible* aRoot, bool aInvalidationRequired = true) :
     mInvalidationRequired(aInvalidationRequired), mRoot(aRoot)
   {
     MOZ_ASSERT(!(mRoot->mStateFlags & Accessible::eSubtreeMutating));
     mRoot->mStateFlags |= Accessible::eSubtreeMutating;
   }
   ~AutoTreeMutation()
   {
     if (mInvalidationRequired)

--- a/accessible/generic/BaseAccessibles.h
+++ b/accessible/generic/BaseAccessibles.h
@@ -113,17 +113,17 @@ protected:
 
 /**
  * A wrapper accessible around native accessible to connect it with
  * crossplatform accessible tree.
  */
 class DummyAccessible : public AccessibleWrap
 {
 public:
-  DummyAccessible(DocAccessible* aDocument = nullptr) :
+  explicit DummyAccessible(DocAccessible* aDocument = nullptr) :
     AccessibleWrap(nullptr, aDocument) { }
 
   virtual uint64_t NativeState() MOZ_OVERRIDE MOZ_FINAL;
   virtual uint64_t NativeInteractiveState() const MOZ_OVERRIDE MOZ_FINAL;
   virtual uint64_t NativeLinkState() const MOZ_OVERRIDE MOZ_FINAL;
   virtual bool NativelyUnavailable() const MOZ_OVERRIDE MOZ_FINAL;
   virtual void ApplyARIAState(uint64_t* aState) const MOZ_OVERRIDE MOZ_FINAL;
 

--- a/accessible/ipc/DocAccessibleChild.h
+++ b/accessible/ipc/DocAccessibleChild.h
@@ -17,17 +17,17 @@ class AccShowEvent;
 
   /*
    * These objects handle content side communication for an accessible document,
    * and their lifetime is the same as the document they represent.
    */
 class DocAccessibleChild : public PDocAccessibleChild
 {
 public:
-  DocAccessibleChild(DocAccessible* aDoc) :
+  explicit DocAccessibleChild(DocAccessible* aDoc) :
     mDoc(aDoc)
   { MOZ_COUNT_CTOR(DocAccessibleChild); }
   ~DocAccessibleChild()
   {
     mDoc->SetIPCDoc(nullptr);
     MOZ_COUNT_DTOR(DocAccessibleChild);
   }
 

--- a/accessible/ipc/DocAccessibleParent.h
+++ b/accessible/ipc/DocAccessibleParent.h
@@ -96,17 +96,17 @@ public:
     mAccessibles.RemoveEntry(aAccessible->ID());
   }
 
 private:
 
   class ProxyEntry : public PLDHashEntryHdr
   {
   public:
-    ProxyEntry(const void*) : mProxy(nullptr) {}
+    explicit ProxyEntry(const void*) : mProxy(nullptr) {}
     ProxyEntry(ProxyEntry&& aOther) :
       mProxy(aOther.mProxy) { aOther.mProxy = nullptr; }
     ~ProxyEntry() { delete mProxy; }
 
     typedef uint64_t KeyType;
     typedef const void* KeyTypePointer;
 
     bool KeyEquals(const void* aKey) const

--- a/accessible/xpcom/xpcAccessibleApplication.h
+++ b/accessible/xpcom/xpcAccessibleApplication.h
@@ -16,17 +16,18 @@ namespace a11y {
 
 /**
  * XPCOM wrapper around ApplicationAccessible class.
  */
 class xpcAccessibleApplication : public xpcAccessibleGeneric,
                                  public nsIAccessibleApplication
 {
 public:
-  xpcAccessibleApplication(Accessible* aIntl) : xpcAccessibleGeneric(aIntl) { }
+  explicit xpcAccessibleApplication(Accessible* aIntl) :
+    xpcAccessibleGeneric(aIntl) { }
 
   NS_DECL_ISUPPORTS_INHERITED
 
   // nsIAccessibleApplication
   NS_IMETHOD GetAppName(nsAString& aName) MOZ_FINAL;
   NS_IMETHOD GetAppVersion(nsAString& aVersion) MOZ_FINAL;
   NS_IMETHOD GetPlatformName(nsAString& aName) MOZ_FINAL;
   NS_IMETHOD GetPlatformVersion(nsAString& aVersion) MOZ_FINAL;

--- a/accessible/xpcom/xpcAccessibleDocument.h
+++ b/accessible/xpcom/xpcAccessibleDocument.h
@@ -19,17 +19,17 @@ namespace a11y {
 
 /**
  * XPCOM wrapper around DocAccessible class.
  */
 class xpcAccessibleDocument : public xpcAccessibleHyperText,
                               public nsIAccessibleDocument
 {
 public:
-  xpcAccessibleDocument(DocAccessible* aIntl) :
+  explicit xpcAccessibleDocument(DocAccessible* aIntl) :
     xpcAccessibleHyperText(aIntl), mCache(kDefaultCacheLength) { }
 
   NS_DECL_ISUPPORTS_INHERITED
   NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(xpcAccessibleDocument,
                                            xpcAccessibleGeneric)
 
   // nsIAccessibleDocument
   NS_IMETHOD GetURL(nsAString& aURL) MOZ_FINAL;

--- a/accessible/xpcom/xpcAccessibleGeneric.h
+++ b/accessible/xpcom/xpcAccessibleGeneric.h
@@ -21,17 +21,17 @@ namespace a11y {
  * XPCOM wrapper around Accessible class.
  */
 class xpcAccessibleGeneric : public xpcAccessible,
                              public xpcAccessibleHyperLink,
                              public xpcAccessibleSelectable,
                              public xpcAccessibleValue
 {
 public:
-  xpcAccessibleGeneric(Accessible* aInternal) :
+  explicit xpcAccessibleGeneric(Accessible* aInternal) :
     mIntl(aInternal), mSupportedIfaces(0)
   {
     if (mIntl->IsSelect())
       mSupportedIfaces |= eSelectable;
     if (mIntl->HasNumericValue())
       mSupportedIfaces |= eValue;
     if (mIntl->IsLink())
       mSupportedIfaces |= eHyperLink;

--- a/accessible/xpcom/xpcAccessibleHyperText.h
+++ b/accessible/xpcom/xpcAccessibleHyperText.h
@@ -18,17 +18,18 @@ namespace mozilla {
 namespace a11y {
 
 class xpcAccessibleHyperText : public xpcAccessibleGeneric,
                                public nsIAccessibleText,
                                public nsIAccessibleEditableText,
                                public nsIAccessibleHyperText
 {
 public:
-  xpcAccessibleHyperText(Accessible* aIntl) : xpcAccessibleGeneric(aIntl)
+  explicit xpcAccessibleHyperText(Accessible* aIntl) :
+    xpcAccessibleGeneric(aIntl)
   {
     if (mIntl->IsHyperText() && mIntl->AsHyperText()->IsTextRole())
       mSupportedIfaces |= eText;
   }
 
   NS_DECL_ISUPPORTS_INHERITED
 
   NS_DECL_NSIACCESSIBLETEXT

--- a/accessible/xpcom/xpcAccessibleImage.h
+++ b/accessible/xpcom/xpcAccessibleImage.h
@@ -13,17 +13,18 @@
 
 namespace mozilla {
 namespace a11y {
 
 class xpcAccessibleImage : public xpcAccessibleGeneric,
                            public nsIAccessibleImage
 {
 public:
-  xpcAccessibleImage(Accessible* aIntl) : xpcAccessibleGeneric(aIntl) { }
+  explicit xpcAccessibleImage(Accessible* aIntl) :
+    xpcAccessibleGeneric(aIntl) { }
 
   NS_DECL_ISUPPORTS_INHERITED
 
   NS_IMETHOD GetImagePosition(uint32_t aCoordType,
                               int32_t* aX, int32_t* aY) MOZ_FINAL;
   NS_IMETHOD GetImageSize(int32_t* aWidth, int32_t* aHeight) MOZ_FINAL;
 
 protected:

--- a/accessible/xpcom/xpcAccessibleTable.h
+++ b/accessible/xpcom/xpcAccessibleTable.h
@@ -15,17 +15,18 @@ namespace a11y {
 
 /**
  * XPCOM wrapper around TableAccessible class.
  */
 class xpcAccessibleTable : public xpcAccessibleGeneric,
                            public nsIAccessibleTable
 {
 public:
-  xpcAccessibleTable(Accessible* aIntl) : xpcAccessibleGeneric(aIntl) { }
+  explicit xpcAccessibleTable(Accessible* aIntl) :
+    xpcAccessibleGeneric(aIntl) { }
 
   NS_DECL_ISUPPORTS_INHERITED
 
   // nsIAccessibleTable
   NS_IMETHOD GetCaption(nsIAccessible** aCaption) MOZ_FINAL;
   NS_IMETHOD GetSummary(nsAString& aSummary) MOZ_FINAL;
   NS_IMETHOD GetColumnCount(int32_t* aColumnCount) MOZ_FINAL;
   NS_IMETHOD GetRowCount(int32_t* aRowCount) MOZ_FINAL;

--- a/accessible/xpcom/xpcAccessibleTableCell.h
+++ b/accessible/xpcom/xpcAccessibleTableCell.h
@@ -16,17 +16,18 @@ namespace a11y {
 
 /**
  * XPCOM wrapper around TableAccessibleCell class.
  */
 class xpcAccessibleTableCell : public xpcAccessibleHyperText,
                                public nsIAccessibleTableCell
 {
 public:
-  xpcAccessibleTableCell(Accessible* aIntl) : xpcAccessibleHyperText(aIntl) { }
+  explicit xpcAccessibleTableCell(Accessible* aIntl) :
+    xpcAccessibleHyperText(aIntl) { }
 
   NS_DECL_ISUPPORTS_INHERITED
 
   // nsIAccessibleTableCell
   NS_IMETHOD GetTable(nsIAccessibleTable** aTable) MOZ_FINAL;
   NS_IMETHOD GetColumnIndex(int32_t* aColIdx) MOZ_FINAL;
   NS_IMETHOD GetRowIndex(int32_t* aRowIdx) MOZ_FINAL;
   NS_IMETHOD GetColumnExtent(int32_t* aExtent) MOZ_FINAL;